US20070041322A1 - Rate adaptation using semi-open loop technique - Google Patents
Rate adaptation using semi-open loop technique Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
- H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0015—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the adaptation strategy
- H04L1/0016—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the adaptation strategy involving special memory structures, e.g. look-up tables
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0204—Channel estimation of multiple channels
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
- H04L47/26—Flow control; Congestion control using explicit feedback to the source, e.g. choke packets
- H04L47/263—Rate modification at the source after receiving feedback
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/26—Measuring noise figure; Measuring signal-to-noise ratio
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/1607—Details of the supervisory signal
Definitions
- the present invention relates to rate adaptation in a wireless environment and in particular to using a semi-open loop technique to achieve an optimized rate.
- rate adaptation can be advantageously used to achieve optimized throughput in a system with multiple PHY (i.e. physical device) rates.
- Rate adaptation is especially important in a multiple-input multiple-output (MIMO) system because the number of streams introduces yet another dimension to the channel condition.
- MIMO multiple-input multiple-output
- the intended receiver estimates some function of its receive signal (e.g. the channel state information (CSI)), and sends it back to the transmitter.
- the transmitter determines the optimized rate for its next transmission based on the feedback from the receiver.
- this closed-loop rate adaptation has significant system overhead associated with determining the appropriate feedback.
- the transmitter uses trial and error to determine an optimized rate.
- the open-loop rate adaptation scheme does not incur any feedback overhead.
- the transmitter receives no feedback from the receiver, the rate is typically slow to change and can result in errors as incorrect rates are selected.
- This system can include first and second nodes in which transmissions from the first node to the second node are on a “downlink channel” and transmissions from the second node to the first node are on an “uplink channel”.
- Each node in the MIMO system can include multiple transmitters and receivers.
- the first node can estimate the uplink channel using a packet sent by the second node to the first node.
- This uplink channel can be transposed to provide an estimated downlink channel.
- the first node can use transmitter and receiver characteristics from both the first and second nodes and the estimated downlink channel to accurately adapt the rate.
- the receiver characteristics can include the sensitivity of the second node.
- using the transmitter and receiver characteristics can include computing a post-detection signal to noise ratio (SNR) of the second node based on the estimated downlink channel, noise floor information from the second node, and a receiver structure of the second node.
- This post-detection SNR can be adjusted with a transmit output power of the second node for a received data rate of the packet.
- an estimated post-detection SNR for each rate at the second node can be computed using the transmitter power per rate of the first node, thereby building a sensitivity table for the second node. If the transmitter EVM is not negligible, then the estimated post-detection SNR for each rate at the second node can be adjusted with a transmitter EVM per power of the first and second nodes.
- the first node can use the sensitivity table to choose the optimized rate.
- using the sensitivity table can include choosing the highest rate whose estimated post-detection SNR is larger than a threshold SNR.
- a node that can quickly and accurately adapting its rate in a MIMO system includes various tables that can be accessed by software with computer-implementable instructions.
- the node can include a table that indicates the post-detection SNR for rates at another node in the MIMO system.
- the node can further include a table that indicates transmitter output power per rate at the node as well as a table that indicates a transmitter EVM per power of the node and the other node.
- the node can further include software with computer-implementable instructions for accessing the above-described tables and performing the above-described steps.
- FIG. 1 illustrates a simplified multiple-input multiple-output (MIMO) system.
- FIG. 2 illustrates one technique that can be used to obtain the transmit power information per data rate.
- FIG. 3 illustrates a technique for accessing and using a transmitter EVM versus transmitter power table.
- FIG. 4 illustrates an exemplary technique that can accurately evaluate the downlink quality of a channel in a MIMO system.
- FIG. 5 illustrates a node including various tables that can be accessed by software with computer-implementable instructions.
- FIG. 1 illustrates a simplified MIMO system 100 in which the semi-open loop rate adaptation technique can be used.
- each transceiver includes a plurality of transmitters (Txs) and receivers (Rxs).
- Txs transmitters
- Rxs receivers
- a first transceiver referenced as node 105 , can include transmitters 101 A and 101 B as well as receivers 102 A and 102 B.
- a second transceiver can include transmitters 103 A and 103 B as well as receivers 104 A and 104 B. Note that each transmitter/receiver pair, e.g. transmitter 101 A/receiver 102 A, shares an antenna.
- MIMO system 100 can divide a data stream into multiple unique streams. Node 105 can modulate each of these multiple streams and then simultaneously transmit each stream through a different antenna in the same frequency channel. By leveraging multipath, i.e. reflections of the signals, each MIMO receive chain of node 106 can be a linear combination of the multiple transmitted data streams. Node 106 can separate these data streams using MIMO algorithms that rely on estimates of the channels between node 105 and 106 .
- a transmission from node 105 to node 106 is referenced herein as a “downlink” whereas a transmission from node 106 to node 105 is referenced as an “uplink”.
- downlink and uplink merely describe the signal flow direction in a physical channel.
- the physical channels between node 105 and node 106 are reciprocal (i.e. exhibit the same characteristics) as long as both downlink and uplink channels use the same frequency.
- node 105 can estimate the uplink channel from the packets sent by node 106 , and transpose it to obtain the downlink channel, as long as the uplink and downlink packet use the same number of streams. For example, if an ACK (acknowledgment) packet is used as the uplink packet, then the ACK packet needs to be sent using the same number of streams as the downlink packet. (Note that an ACK packet may be sent using a data rate lower than that used to transmit a data packet. Additionally, the ACK packet may or may not be sent using the same power that is typically used for this lower rate.)
- ACK acknowledgenowledgment
- the radio frequency (RF) circuits in nodes 105 and 106 may not be.
- the optimized rate for the downlink from node 105 to node 106 should be a function of transmitter 101 A/ 101 B, the channel from node 105 to node 106 , and receiver 104 A/ 104 B.
- the optimized rate of the uplink measured at node 105 should be a function of transmitter 103 A/ 103 B, the channel from node 106 to node 105 , and receiver 102 A/ 102 B.
- node 105 can use the transmitter and receiver characteristics of both nodes 105 and 106 to estimate the uplink quality and then compute the equivalent downlink quality.
- Nodes 105 and 106 can exchange these transmitter and receiver characteristics initially and/or periodically.
- the transmitter characteristics can include the transmitter output power per data rate and the transmitter EVM (error vector magnitude) per transmitter output power.
- the power amplifiers of transmitters 101 A/ 101 B (node 105 ) and 103 A/ 103 B (node 106 ) may be asymmetrical, thereby resulting in different transmit powers delivered by each node.
- the transmit power of a power amplifier can vary per rate and the tolerance of power amplifier non-linearity can depend on the data rate as well as power amplifier implementation specifics. Therefore, to accurately capture the equivalent downlink quality by estimating the uplink quality, node 105 should know the transmit power information per data rate for node 106 .
- FIG. 2 illustrates one technique 200 that can be used to obtain the transmit power information per data rate.
- step 201 an initial table of transmitter power per data rate can be accessed.
- this table can include the worst-case output power vs. rate characteristics. These characteristics can be determined through lab bench testing, for example. Therefore, in one embodiment, this information can be created in step 201 . In another embodiment, a vendor can provide this information, thereby allowing immediate use of the table.
- this table can be slowly adapted, if necessary, based on receiver RSSI (receiver signal strength indicator) measurements. For example, in one embodiment, the transmit power for the highest rate can be reduced if an ACK RSSI is more than enough to improve a transmit EVM.
- receiver RSSI receiver signal strength indicator
- step 203 the transmit power information per data rate tables at the two nodes can be exchanged. That is, the downlink/uplink designation shown in FIG. 1 is from the perspective of node 105 . An opposite relationship can be defined from the perspective of node 106 . Thus, steps 201 , 202 , and 203 can be performed at each node in the wireless network. In one embodiment, the transmit power per data rate tables can be exchanged at an initial link setup. In another embodiment, these tables can be updated periodically during operation of the wireless network. Table 1 indicates exemplary transmit powers for various data rates (referenced as MCS 0 -MCS 7 ). TABLE 1 Transmit Power Per Data Rate Transmit Power Data Rate (MCS) (dBm) MCS0 20 MCS1 20 MCS2 20 MCS3 18 MCS4 18 MCS5 17 MCS6 15 MCS7 14
- MCS Power Per Data Rate Transmit Power Data Rate
- transmitter EVM per transmitter output power the transmitter EVM generally depends on the transmit power due to power amplifier non-linearity. Because transmitter EVM per transmit power is determined by the characteristics of the power amplifier and each node can use different power amplifiers, transmitter EVM information per transmit power can also be exchanged in one embodiment of the invention.
- FIG. 3 illustrates a technique 300 for accessing and using a transmitter EVM versus transmitter power table.
- a transmitter EVM vs. transmitter power table can be accessed.
- the transmitter EVM vs. transmitter power table can be created during manufacturing.
- this transmitter EVM vs. transmitter power table can include a temperature variation lookup.
- a temperature sensor can be positioned close to the power amplifier. The temperature difference between the sensor temperature and the room temperature (or, alternatively, the temperature at which the manufacturing calibration was done) can be used to lookup the EVM difference.
- the information in the transmitter EVM vs. transmitter power table can include an initial table based on the calibration temperature, a temperature correction table, and a current temperature.
- part-to-part temperature variations can be calibrated during manufacturing, and an average temperature characteristic can be used for all parts. In this manner, only one temperature correction table, based on average temperature characteristics, need be generated.
- step 301 can include a continuous calibration during operation of the device. For example, if feedback from the receiver node is supported, then an EVM can be measured at the receiver node any time a packet is transmitted at any output power level. In one embodiment, to build a complete transmitter EVM vs. transmitter power table, the transmissions can cover all the possible output power levels being used within a given time window (during which the temperature change is negligible).
- the tables can be exchanged at an initial link setup between the nodes.
- the transmitter EVM vs. transmitter power table can be updated periodically during operation of the wireless network.
- Table 2 indicates EVMs for various data rates (referenced as MCS 0 -MCS 7 ). TABLE 2 EVM Per Data Rate Transmit power Data Rate (MCS) (dBm) MCS0 ⁇ 5 MCS1 ⁇ 10 MCS2 ⁇ 13 MCS3 ⁇ 16 MCS4 ⁇ 19 MCS5 ⁇ 22 MCS6 ⁇ 25 MCS7 ⁇ 27 Receiver Characteristics
- the receiver sensitivity which can be defined as performance per rate, can also be exchanged.
- the receiver architecture can determine the ease of defining the sensitivity for MIMO systems.
- the SNR per stream can be defined after-an equalizer in the receiver chain, which is sometimes called “post-detection SNR”, which advantageously measures the effect of the equalizer.
- the post-detection SNR per stream can be calculated from the channel and the noise floor with a priori knowledge of the MIMO receiver. For example, if a linear receiver including an MMSE (minimum mean square error) detector is used, the post-detection SNR per stream can be derived as follows.
- MMSE minimum mean square error
- ⁇ 2 is the noise variance at a receiver of node 106 .
- R e,i is the i th diagonal element.
- R e is an N ⁇ N matrix where N is the number of streams and the diagonal elements of the matrix are elements (1,1), (2,2), . . . (N,N) of R e .)
- the receiver sensitivity per rate table can be defined as the post-detection SNR per rate for a given PER (packet error rate). This table can be obtained through lab bench testing or updated periodically based on packet error statistics. In one embodiment, the receiver sensitivity per rate table can be divided into two parts: (1) post-detection SNR to SNR at the decision (i.e. the demodulator) device, and (2) the SNR at the decision device per rate for a given PER.
- the second mapping can be obtained by simulations and/or lab bench testing, and will be updated periodically based on packet error statistics.
- the SNR at the decision device can be important because the post-detection SNR may not represent the full effects of circuit impairments (e.g. dynamic range, phase noise, etc.).
- the SNR at the decision device can be measured either by computing EVM with pilots (known signals) or by computing EVM with the data.
- FIG. 4 illustrates an exemplary technique 400 that node 105 ( FIG. 1 ) can use to evaluate the link quality from node 105 to node 106 (i.e. the downlink quality) by estimating the link quality from node 106 to node 105 (i.e. the uplink quality).
- node 105 can calibrate the differences in Tx/Rx characteristics between node 105 and node 106 to assess a more accurate downlink quality.
- node 105 can estimate the uplink channel using channel estimation (i.e. CSI) based on the preamble (i.e. training fields).
- channel estimation i.e. CSI
- node 105 can transpose the estimated uplink channel (i.e. by making row elements into column elements and vice versa) to get the downlink channel.
- node 105 can compute the post-detection SNR of node 106 based on the downlink channel, the noise floor information of node 106 (as measure by node 106 and provided to node 105 ), and the receiver structure of node 106 (e.g. like the type of channel equalizer: MMSE equalizer or ZF equalizer, or another type of structure).
- node 105 can adjust the computed post-detection SNR with the transmitter output power of node 106 for the received data rate.
- node 105 can compute the post-detection SNR for each rate at node 106 with the transmitter power per rate table of node 105 , thereby building a sensitivity table for node 106 .
- node 105 can adjust the estimated post-detection SNR for each rate at node 106 with the transmitter EVM per power tables of node 105 and node 106 , if necessary (e.g. when the transmitter EVM is not negligible (e.g.
- node 105 can choose the optimized rate by referring to the post-detection SNR per rate table of node 106 .
- the optimized rate is the highest rate whose estimated post-detection SNR is larger than the required (i.e. the minimum SNR to get to less than 10% PER).
- FIG. 5 illustrates a node 500 including various tables that can be accessed by software with computer-implementable instructions.
- node 500 can include a table 501 that indicates the post-detection SNR for rates at node 106 ( FIG. 1 ). This table is also called a sensitivity table herein.
- Node 500 can further include a table 502 , which indicates transmitter output power per rate at node 105 , as well as a table 503 , which indicates a transmitter EVM per power of nodes 105 and 106 .
- Tables 501 , 502 , 503 can be stored using any standard memory devices or structures.
- node 500 can further include software 504 with computer-implementable instructions (residing on a computer-readable medium) for accessing tables 501 , 502 , and 503 and performing technique 400 ( FIG. 4 ).
- probing can be advantageously used to determine the optimized number of streams for the MIMO system, the guard intervals to be used for the packets forming those streams, and the bandwidth (i.e. 20/40 MHz) to be used.
- the choice of the number of streams can significantly affect the success of rate adaptation.
- conventional channel estimation can readily determine that reducing the number of streams is appropriate.
- determining whether increasing the number of stream is appropriate can be difficult using standard techniques.
- additional channel estimation can be performed using probes to determine if increasing the number of streams is appropriate. For example, to obtain more channel information, a device can periodically probe for a larger number of streams. As described above, if the uplink packet (e.g. an ACK packet) always uses the same number of streams as the downlink packet (e.g. a data packet), then the reverse channel can be advantageously estimated.
- the uplink packet e.g. an ACK packet
- the downlink packet e.g. a data packet
- Orthogonal frequency division multiplexing can advantageously reduce multipath distortion in a MIMO system.
- the densely packed subcarriers in the MIMO system are orthogonal to ensure non-interference even under multipath conditions.
- An OFDM symbol includes a fast Fourier transform (FFT) interval (from which the data is extracted) preceded by a guard interval.
- FFT fast Fourier transform
- the guard interval can advantageously serve as a repository for echoes from the previous symbol, thereby preventing such echoes from adversely affecting the subsequent FFT interval.
- the guard interval can be 800 ns in duration, which is commensurate with the longest indoor multipath.
- the guard interval can be 400 ns in duration, which is commensurate with the longest indoor multipath of a home or small office environment. In yet another embodiment, the guard interval can be 1600 ns in duration, which is commensurate with the longest outdoor multipath. As used herein, the terms “half guard interval” and “full guard interval” refer to the 400 ns and 800 ns durations.
- a rate table of various rates and their associated guard intervals can be developed over time. That is, the choice of guard interval can be different for each data rate because different data rates will have different sensitivities to multipath. Note that this rate table will depend on the environment, although the delay spread is assumed to be unchanged during the period. For example, in contrast to an outdoor environment, an indoor environment is relatively static.
- the guard interval choice can be determined by either measuring the channel flatness (e.g. how correlated is the channel from one bin to another bin. If the delay spread is small, then the channel variation is small. For example, a “0” delay spread channel is flat in the frequency domain. On the other hand, if the delay spread is large, then the channel varies significantly from bin to bin) directly (e.g. using channel estimations) and using this measurement as an index to determine which rates should use full guard intervals or reduced guard intervals.
- packets can be sent with both full and reduced guard intervals. At this point, the EVMs associated with those packets and then the EVM difference between those two packets can be measured. The EVM difference can be used to determine if the impact to the EVM is sufficient to preclude the use of the most effective rates.
- the receiver that receives the packets can make this determination and provide feedback in a closed loop manner to the transmitter.
- reciprocity can be used such that the uplink packets always use the same guard interval setting.
- the transmitter can estimate the flatness or EVM of the uplink packets when the downlink packets are sent using a different guard interval.
- each frequency band includes a predetermined number of frequency channels.
- the 2.4 GHz frequency band includes 14 channels, wherein each channel when occupied has a 22 MHz bandwidth and the center frequencies of adjacent channels are 5 MHz apart.
- 5 GHz frequency band includes 12 channels, wherein each channel when occupied has a 20 MHz bandwidth and the center frequencies of adjacent channels are 20 MHz apart.
- a 40 MHz channel always has greater capacity than a 20 MHz channel, and increasingly so as the signal to noise ratio (SNR) increases.
- SNR signal to noise ratio
- the 20/40 MHz decision can be separate from the rate adaptation determination. There are three modes of operations: 40 MHz, mixed 40 MHz/20 MHz, and 20 MHz.
- the device can operate in the 40 MHz mode.
- the receiver can perform dynamic 20/40 MHz detection on a packet-by-packet basis.
- the transmitter can transmit 40 MHz packets unless certain conditions exist (e.g. the MAC times out due to 40 MHz CCA busy or multi-rate retry to send failing 40 MHz packets at 20 MHz). Note that 6 Mbps and 20 MHz is currently the last rate in the rate table.
- the device can operate in the mixed 20/40 MHz mode.
- the receiver can perform dynamic 20/40 MHz detection on a packet-by-packet basis. Note that although the transmitter can transmit 20 MHz packets, the carrier frequency can be set as if for 40 MHz transmission.
- the device can operate solely in the 20 MHz mode.
- the carrier frequency can be set at the middle of the 20 MHz band, the receiver only detects 20 MHz packets, and the transmitter transmits only 20 MHz packets.
- Switching between modes can be based on the long term sensing of extension channel activity. In one embodiment, switching between modes can be limited to be between the 40 MHz mode and the 40/20 MHz mixed mode or, alternatively, between the 40/20 MHz mixed mode and the 20 MHz mode.
Abstract
Description
- This application claims priority of U.S. Provisional Patent Application 60/643,459, entitled “Rate Adaptation Using Semi-Open Loop Techniques” filed Jan. 12, 2005.
- 1. Field of the Invention
- The present invention relates to rate adaptation in a wireless environment and in particular to using a semi-open loop technique to achieve an optimized rate.
- 2. Related Art
- Because the condition of a channel in a wireless environment varies over time, rate adaptation can be advantageously used to achieve optimized throughput in a system with multiple PHY (i.e. physical device) rates. Rate adaptation is especially important in a multiple-input multiple-output (MIMO) system because the number of streams introduces yet another dimension to the channel condition. In general, there are two categories of rate adaptation techniques: a closed-loop rate adaptation and an open-loop rate adaptation.
- In the closed-loop rate adaptation, the intended receiver estimates some function of its receive signal (e.g. the channel state information (CSI)), and sends it back to the transmitter. The transmitter determines the optimized rate for its next transmission based on the feedback from the receiver. Unfortunately, this closed-loop rate adaptation has significant system overhead associated with determining the appropriate feedback.
- In the open-loop rate adaptation, the transmitter uses trial and error to determine an optimized rate. Thus, the open-loop rate adaptation scheme does not incur any feedback overhead. However, because the transmitter receives no feedback from the receiver, the rate is typically slow to change and can result in errors as incorrect rates are selected.
- Therefore, a need arises for a fast and accurate rate adaptation technique that minimizes system overhead.
- A method for quickly and accurately adapting a rate in a multiple-input multiple-output (MIMO) system while minimizing system overhead is described. This system can include first and second nodes in which transmissions from the first node to the second node are on a “downlink channel” and transmissions from the second node to the first node are on an “uplink channel”. Each node in the MIMO system can include multiple transmitters and receivers.
- In this method, the first node can estimate the uplink channel using a packet sent by the second node to the first node. This uplink channel can be transposed to provide an estimated downlink channel. The first node can use transmitter and receiver characteristics from both the first and second nodes and the estimated downlink channel to accurately adapt the rate. Notably, the receiver characteristics can include the sensitivity of the second node.
- In one embodiment, using the transmitter and receiver characteristics can include computing a post-detection signal to noise ratio (SNR) of the second node based on the estimated downlink channel, noise floor information from the second node, and a receiver structure of the second node. This post-detection SNR can be adjusted with a transmit output power of the second node for a received data rate of the packet. After the adjusting, an estimated post-detection SNR for each rate at the second node can be computed using the transmitter power per rate of the first node, thereby building a sensitivity table for the second node. If the transmitter EVM is not negligible, then the estimated post-detection SNR for each rate at the second node can be adjusted with a transmitter EVM per power of the first and second nodes.
- The first node can use the sensitivity table to choose the optimized rate. In one embodiment, using the sensitivity table can include choosing the highest rate whose estimated post-detection SNR is larger than a threshold SNR.
- A node that can quickly and accurately adapting its rate in a MIMO system is also described. This node includes various tables that can be accessed by software with computer-implementable instructions. Specifically, the node can include a table that indicates the post-detection SNR for rates at another node in the MIMO system. The node can further include a table that indicates transmitter output power per rate at the node as well as a table that indicates a transmitter EVM per power of the node and the other node. Notably, the node can further include software with computer-implementable instructions for accessing the above-described tables and performing the above-described steps.
-
FIG. 1 illustrates a simplified multiple-input multiple-output (MIMO) system. -
FIG. 2 illustrates one technique that can be used to obtain the transmit power information per data rate. -
FIG. 3 illustrates a technique for accessing and using a transmitter EVM versus transmitter power table. -
FIG. 4 illustrates an exemplary technique that can accurately evaluate the downlink quality of a channel in a MIMO system. -
FIG. 5 illustrates a node including various tables that can be accessed by software with computer-implementable instructions. - In a semi-open loop rate adaptation scheme for a multiple-input multiple-output (MIMO) system, a transmitter can advantageously use one or more quality metrics of an uplink as well as knowledge of transmitter/receiver characteristics of both nodes to perform fast and accurate rate adaptation.
FIG. 1 illustrates asimplified MIMO system 100 in which the semi-open loop rate adaptation technique can be used. InMIMO system 100, each transceiver includes a plurality of transmitters (Txs) and receivers (Rxs). For example, a first transceiver, referenced asnode 105, can includetransmitters receivers node 106, can includetransmitters receivers e.g. transmitter 101A/receiver 102A, shares an antenna. - MIMO
system 100 can divide a data stream into multiple unique streams.Node 105 can modulate each of these multiple streams and then simultaneously transmit each stream through a different antenna in the same frequency channel. By leveraging multipath, i.e. reflections of the signals, each MIMO receive chain ofnode 106 can be a linear combination of the multiple transmitted data streams.Node 106 can separate these data streams using MIMO algorithms that rely on estimates of the channels betweennode - For purposes of understanding the semi-loop rate adaptation technique, a transmission from
node 105 tonode 106 is referenced herein as a “downlink” whereas a transmission fromnode 106 tonode 105 is referenced as an “uplink”. Note that the terms downlink and uplink merely describe the signal flow direction in a physical channel. Notably, the physical channels betweennode 105 andnode 106 are reciprocal (i.e. exhibit the same characteristics) as long as both downlink and uplink channels use the same frequency. In a mathematical notation, channel reciprocity is represented by HD=HU T, where HD is the downlink channel (i.e. fromnode 105 to node 106), and HU is the uplink channel (i.e. fromnode 106 to node 105). - With channel reciprocity,
node 105 can estimate the uplink channel from the packets sent bynode 106, and transpose it to obtain the downlink channel, as long as the uplink and downlink packet use the same number of streams. For example, if an ACK (acknowledgment) packet is used as the uplink packet, then the ACK packet needs to be sent using the same number of streams as the downlink packet. (Note that an ACK packet may be sent using a data rate lower than that used to transmit a data packet. Additionally, the ACK packet may or may not be sent using the same power that is typically used for this lower rate.) - Notably, while the physical channel is reciprocal, the radio frequency (RF) circuits in
nodes node 105 tonode 106 should be a function oftransmitter 101A/101B, the channel fromnode 105 tonode 106, andreceiver 104A/104B. In contrast, the optimized rate of the uplink measured atnode 105 should be a function oftransmitter 103A/103B, the channel fromnode 106 tonode 105, andreceiver 102A/102B. - Therefore, in accordance with one aspect of the invention,
node 105 can use the transmitter and receiver characteristics of bothnodes Nodes - Transmitter Characteristics
- In one embodiment, the transmitter characteristics can include the transmitter output power per data rate and the transmitter EVM (error vector magnitude) per transmitter output power. With respect to transmitter output power, the power amplifiers of
transmitters 101A/101B (node 105) and 103A/103B (node 106) may be asymmetrical, thereby resulting in different transmit powers delivered by each node. Moreover, to add complexity to this asymmetry, the transmit power of a power amplifier can vary per rate and the tolerance of power amplifier non-linearity can depend on the data rate as well as power amplifier implementation specifics. Therefore, to accurately capture the equivalent downlink quality by estimating the uplink quality,node 105 should know the transmit power information per data rate fornode 106. -
FIG. 2 illustrates onetechnique 200 that can be used to obtain the transmit power information per data rate. In step 201, an initial table of transmitter power per data rate can be accessed. In one embodiment, this table can include the worst-case output power vs. rate characteristics. These characteristics can be determined through lab bench testing, for example. Therefore, in one embodiment, this information can be created in step 201. In another embodiment, a vendor can provide this information, thereby allowing immediate use of the table. - In
step 202, this table can be slowly adapted, if necessary, based on receiver RSSI (receiver signal strength indicator) measurements. For example, in one embodiment, the transmit power for the highest rate can be reduced if an ACK RSSI is more than enough to improve a transmit EVM. - In
step 203, the transmit power information per data rate tables at the two nodes can be exchanged. That is, the downlink/uplink designation shown inFIG. 1 is from the perspective ofnode 105. An opposite relationship can be defined from the perspective ofnode 106. Thus, steps 201, 202, and 203 can be performed at each node in the wireless network. In one embodiment, the transmit power per data rate tables can be exchanged at an initial link setup. In another embodiment, these tables can be updated periodically during operation of the wireless network. Table 1 indicates exemplary transmit powers for various data rates (referenced as MCS0-MCS7).TABLE 1 Transmit Power Per Data Rate Transmit Power Data Rate (MCS) (dBm) MCS0 20 MCS1 20 MCS2 20 MCS3 18 MCS4 18 MCS5 17 MCS6 15 MCS7 14 - With respect to transmitter EVM per transmitter output power, the transmitter EVM generally depends on the transmit power due to power amplifier non-linearity. Because transmitter EVM per transmit power is determined by the characteristics of the power amplifier and each node can use different power amplifiers, transmitter EVM information per transmit power can also be exchanged in one embodiment of the invention.
-
FIG. 3 illustrates atechnique 300 for accessing and using a transmitter EVM versus transmitter power table. In step 301, a transmitter EVM vs. transmitter power table can be accessed. In one embodiment, the transmitter EVM vs. transmitter power table can be created during manufacturing. - Note that this transmitter EVM vs. transmitter power table can include a temperature variation lookup. To use this temperature variation lookup, a temperature sensor can be positioned close to the power amplifier. The temperature difference between the sensor temperature and the room temperature (or, alternatively, the temperature at which the manufacturing calibration was done) can be used to lookup the EVM difference.
- In one embodiment, the information in the transmitter EVM vs. transmitter power table can include an initial table based on the calibration temperature, a temperature correction table, and a current temperature. In one embodiment, part-to-part temperature variations can be calibrated during manufacturing, and an average temperature characteristic can be used for all parts. In this manner, only one temperature correction table, based on average temperature characteristics, need be generated.
- In another embodiment, step 301 can include a continuous calibration during operation of the device. For example, if feedback from the receiver node is supported, then an EVM can be measured at the receiver node any time a packet is transmitted at any output power level. In one embodiment, to build a complete transmitter EVM vs. transmitter power table, the transmissions can cover all the possible output power levels being used within a given time window (during which the temperature change is negligible).
- In
step 302, the tables can be exchanged at an initial link setup between the nodes. In one embodiment, the transmitter EVM vs. transmitter power table can be updated periodically during operation of the wireless network. - Note that the above-described transmitter output power per data rate table and the transmitter EVM per transmitter output power table can be combined into a single transmitter EVM per data rate table. Table 2 indicates EVMs for various data rates (referenced as MCS0-MCS7).
TABLE 2 EVM Per Data Rate Transmit power Data Rate (MCS) (dBm) MCS0 −5 MCS1 −10 MCS2 −13 MCS3 −16 MCS4 −19 MCS5 −22 MCS6 −25 MCS7 −27
Receiver Characteristics - In accordance with one aspect of the invention, the receiver sensitivity, which can be defined as performance per rate, can also be exchanged. Note that the receiver architecture can determine the ease of defining the sensitivity for MIMO systems. In one embodiment, the SNR per stream can be defined after-an equalizer in the receiver chain, which is sometimes called “post-detection SNR”, which advantageously measures the effect of the equalizer.
- The post-detection SNR per stream can be calculated from the channel and the noise floor with a priori knowledge of the MIMO receiver. For example, if a linear receiver including an MMSE (minimum mean square error) detector is used, the post-detection SNR per stream can be derived as follows.
- In the downlink transmission from
node 105 tonode 106, the error covariance matrix of the linear MMSE receiver atnode 106 can be defined by the equation:
R e=δ2(H D *H D+δ2 I)−1 - where δ2 is the noise variance at a receiver of
node 106. - The post-detection SNR for a stream i can then be computed using the equation:
- where re,i is the ith diagonal element. (Note that Re is an N×N matrix where N is the number of streams and the diagonal elements of the matrix are elements (1,1), (2,2), . . . (N,N) of Re.)
- The receiver sensitivity per rate table can be defined as the post-detection SNR per rate for a given PER (packet error rate). This table can be obtained through lab bench testing or updated periodically based on packet error statistics. In one embodiment, the receiver sensitivity per rate table can be divided into two parts: (1) post-detection SNR to SNR at the decision (i.e. the demodulator) device, and (2) the SNR at the decision device per rate for a given PER. A simple form of the first mapping could be a linear function with clipping (i.e. y=min(x,y_max), where y_max is the maximum SNR achievable in the system given the implementation loss). The second mapping can be obtained by simulations and/or lab bench testing, and will be updated periodically based on packet error statistics.
- Note that the SNR at the decision device can be important because the post-detection SNR may not represent the full effects of circuit impairments (e.g. dynamic range, phase noise, etc.). The SNR at the decision device can be measured either by computing EVM with pilots (known signals) or by computing EVM with the data.
- Rate Adaptation
-
FIG. 4 illustrates anexemplary technique 400 that node 105 (FIG. 1 ) can use to evaluate the link quality fromnode 105 to node 106 (i.e. the downlink quality) by estimating the link quality fromnode 106 to node 105 (i.e. the uplink quality). Intechnique 400, while relying on channel reciprocity,node 105 can calibrate the differences in Tx/Rx characteristics betweennode 105 andnode 106 to assess a more accurate downlink quality. - In
step 401,node 105 can estimate the uplink channel using channel estimation (i.e. CSI) based on the preamble (i.e. training fields). Instep 402,node 105 can transpose the estimated uplink channel (i.e. by making row elements into column elements and vice versa) to get the downlink channel. Instep 403,node 105 can compute the post-detection SNR ofnode 106 based on the downlink channel, the noise floor information of node 106 (as measure bynode 106 and provided to node 105), and the receiver structure of node 106 (e.g. like the type of channel equalizer: MMSE equalizer or ZF equalizer, or another type of structure). In step 404,node 105 can adjust the computed post-detection SNR with the transmitter output power ofnode 106 for the received data rate. In step 405,node 105 can compute the post-detection SNR for each rate atnode 106 with the transmitter power per rate table ofnode 105, thereby building a sensitivity table fornode 106. In step 406 (in one embodiment, an optional step),node 105 can adjust the estimated post-detection SNR for each rate atnode 106 with the transmitter EVM per power tables ofnode 105 andnode 106, if necessary (e.g. when the transmitter EVM is not negligible (e.g. if the EVM is more than 10 dB below the SNR). Instep 407,node 105 can choose the optimized rate by referring to the post-detection SNR per rate table ofnode 106. In one embodiment, the optimized rate is the highest rate whose estimated post-detection SNR is larger than the required (i.e. the minimum SNR to get to less than 10% PER). -
FIG. 5 illustrates anode 500 including various tables that can be accessed by software with computer-implementable instructions. Specifically,node 500 can include a table 501 that indicates the post-detection SNR for rates at node 106 (FIG. 1 ). This table is also called a sensitivity table herein.Node 500 can further include a table 502, which indicates transmitter output power per rate atnode 105, as well as a table 503, which indicates a transmitter EVM per power ofnodes node 500 can further includesoftware 504 with computer-implementable instructions (residing on a computer-readable medium) for accessing tables 501, 502, and 503 and performing technique 400 (FIG. 4 ). - Miscellaneous Probing
- In accordance with one aspect of the invention, probing can be advantageously used to determine the optimized number of streams for the MIMO system, the guard intervals to be used for the packets forming those streams, and the bandwidth (i.e. 20/40 MHz) to be used.
- The choice of the number of streams can significantly affect the success of rate adaptation. Notably, conventional channel estimation can readily determine that reducing the number of streams is appropriate. However, determining whether increasing the number of stream is appropriate can be difficult using standard techniques. In one embodiment, additional channel estimation can be performed using probes to determine if increasing the number of streams is appropriate. For example, to obtain more channel information, a device can periodically probe for a larger number of streams. As described above, if the uplink packet (e.g. an ACK packet) always uses the same number of streams as the downlink packet (e.g. a data packet), then the reverse channel can be advantageously estimated.
- Orthogonal frequency division multiplexing (OFDM) can advantageously reduce multipath distortion in a MIMO system. Specifically, the densely packed subcarriers in the MIMO system are orthogonal to ensure non-interference even under multipath conditions. An OFDM symbol includes a fast Fourier transform (FFT) interval (from which the data is extracted) preceded by a guard interval. The guard interval can advantageously serve as a repository for echoes from the previous symbol, thereby preventing such echoes from adversely affecting the subsequent FFT interval. In one embodiment, the guard interval can be 800 ns in duration, which is commensurate with the longest indoor multipath. In another embodiment, the guard interval can be 400 ns in duration, which is commensurate with the longest indoor multipath of a home or small office environment. In yet another embodiment, the guard interval can be 1600 ns in duration, which is commensurate with the longest outdoor multipath. As used herein, the terms “half guard interval” and “full guard interval” refer to the 400 ns and 800 ns durations.
- Because determining the appropriate guard interval is based on the operating environment (i.e. the delay spread of the channel) rather than fading, a rate table of various rates and their associated guard intervals can be developed over time. That is, the choice of guard interval can be different for each data rate because different data rates will have different sensitivities to multipath. Note that this rate table will depend on the environment, although the delay spread is assumed to be unchanged during the period. For example, in contrast to an outdoor environment, an indoor environment is relatively static.
- In one embodiment, the guard interval choice can be determined by either measuring the channel flatness (e.g. how correlated is the channel from one bin to another bin. If the delay spread is small, then the channel variation is small. For example, a “0” delay spread channel is flat in the frequency domain. On the other hand, if the delay spread is large, then the channel varies significantly from bin to bin) directly (e.g. using channel estimations) and using this measurement as an index to determine which rates should use full guard intervals or reduced guard intervals. In another embodiment, packets can be sent with both full and reduced guard intervals. At this point, the EVMs associated with those packets and then the EVM difference between those two packets can be measured. The EVM difference can be used to determine if the impact to the EVM is sufficient to preclude the use of the most effective rates.
- In one embodiment, the receiver that receives the packets can make this determination and provide feedback in a closed loop manner to the transmitter. In another embodiment, reciprocity can be used such that the uplink packets always use the same guard interval setting. In this case, the transmitter can estimate the flatness or EVM of the uplink packets when the downlink packets are sent using a different guard interval.
- According to the IEEE 802.11 family of standards, which governs wireless communications, each frequency band includes a predetermined number of frequency channels. For example, the 2.4 GHz frequency band includes 14 channels, wherein each channel when occupied has a 22 MHz bandwidth and the center frequencies of adjacent channels are 5 MHz apart. In contrast, 5 GHz frequency band includes 12 channels, wherein each channel when occupied has a 20 MHz bandwidth and the center frequencies of adjacent channels are 20 MHz apart.
- Notably, using a wider channel could advantageously increase capacity, i.e. the transfer rate. Specifically, a 40 MHz channel always has greater capacity than a 20 MHz channel, and increasingly so as the signal to noise ratio (SNR) increases. In one embodiment, the 20/40 MHz decision can be separate from the rate adaptation determination. There are three modes of operations: 40 MHz, mixed 40 MHz/20 MHz, and 20 MHz.
- If no or minimal interference is present on the extension channel, then the device can operate in the 40 MHz mode. In this case, the receiver can perform dynamic 20/40 MHz detection on a packet-by-packet basis. In this mode, the transmitter can transmit 40 MHz packets unless certain conditions exist (e.g. the MAC times out due to 40 MHz CCA busy or multi-rate retry to send failing 40 MHz packets at 20 MHz). Note that 6 Mbps and 20 MHz is currently the last rate in the rate table.
- If weak interference exists on the extension channel, then the device can operate in the mixed 20/40 MHz mode. In this case, the receiver can perform dynamic 20/40 MHz detection on a packet-by-packet basis. Note that although the transmitter can transmit 20 MHz packets, the carrier frequency can be set as if for 40 MHz transmission.
- If heavy interference exists on the extension channel, then the device can operate solely in the 20 MHz mode. In this case, the carrier frequency can be set at the middle of the 20 MHz band, the receiver only detects 20 MHz packets, and the transmitter transmits only 20 MHz packets.
- Switching between modes can be based on the long term sensing of extension channel activity. In one embodiment, switching between modes can be limited to be between the 40 MHz mode and the 40/20 MHz mixed mode or, alternatively, between the 40/20 MHz mixed mode and the 20 MHz mode.
- Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying figures, it is to be understood that the invention is not limited to those precise embodiments. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. As such, many modifications and variations will be apparent. For example, although a MIMO system is discussed in detail herein,
semi-open technique 400 can be readily suited for any time division duplex (TDD) system. Accordingly, it is intended that the scope of the invention be defined by the following Claims and their equivalents.
Claims (22)
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Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20070298810A1 (en) * | 2006-06-27 | 2007-12-27 | Assaf Kasher | Selective 40 MHz Operation in 2.4 GHz Band |
US20080167063A1 (en) * | 2007-01-05 | 2008-07-10 | Saishankar Nandagopalan | Interference mitigation mechanism to enable spatial reuse in uwb networks |
US20080225761A1 (en) * | 2007-03-13 | 2008-09-18 | Ning Zhang | Estimating Timing And Frequency Information For Multiple Channel Wireless Communication Systems |
US20090052319A1 (en) * | 2006-06-30 | 2009-02-26 | Alaa Muqattash | Reservation based mac protocol |
US20090202014A1 (en) * | 2008-02-11 | 2009-08-13 | Syed Aon Mujtaba | Adaptation Techniques in MIMO |
US20090310590A1 (en) * | 2004-08-18 | 2009-12-17 | William Kish | Transmission and Reception Parameter Control |
US20100238913A1 (en) * | 2009-03-23 | 2010-09-23 | Futurewei Technologies, Inc. | Adaptive Precoding Codebooks for Wireless Communications |
US8218690B1 (en) | 2008-09-29 | 2012-07-10 | Qualcomm Atheros, Inc. | Timing offset compensation for high throughput channel estimation |
US20140204776A1 (en) * | 2013-01-23 | 2014-07-24 | Academia Sinica | Dynamic Adaption of Transmission Rate for Multiuser MIMO Networks |
US9124328B2 (en) | 2009-03-12 | 2015-09-01 | Futurewei Technologies, Inc. | System and method for channel information feedback in a wireless communications system |
DE102014208084A1 (en) * | 2014-04-29 | 2015-10-29 | Volkswagen Aktiengesellschaft | Estimate a reception probability of a data packet and a transmission rate for data packets |
US20160381701A1 (en) * | 2015-06-29 | 2016-12-29 | T-Mobile Usa, Inc. | Channel Coding for Real Time Wireless Traffic |
US9749023B2 (en) * | 2008-04-28 | 2017-08-29 | Apple Inc. | Apparatus and methods for transmission and reception of data in multi-antenna systems |
US10771185B1 (en) | 2019-02-19 | 2020-09-08 | Samsung Electronics Co., Ltd. | System and method for setting link parameters in a WiFi link |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101637798B1 (en) | 2006-10-03 | 2016-07-07 | 인터디지탈 테크날러지 코포레이션 | Combined open loop/closed loop (cqi-based) uplink transmit power control with interference mitigation for e-utra |
MY151945A (en) | 2007-03-07 | 2014-07-31 | Interdigital Tech Corp | Combined open loop/closed loop method for controlling uplink power of a mobile station |
CN102355432B (en) * | 2011-08-12 | 2014-07-02 | 福建星网锐捷网络有限公司 | Method and base station for determining wireless message transmission rate |
US20170171780A1 (en) * | 2015-12-14 | 2017-06-15 | Qualcomm Incorporated | Techniques for adapting a rate of data transmission |
US20230163813A1 (en) * | 2020-04-10 | 2023-05-25 | Lenovo (Singapore) Pte. Ltd. | Method and Apparatus Including Error Vector Magnitude Definition and Testing for Antenna Ports and Multi-Layer Transmissions |
Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6452348B1 (en) * | 1999-11-30 | 2002-09-17 | Sony Corporation | Robot control device, robot control method and storage medium |
US20030022686A1 (en) * | 2001-06-29 | 2003-01-30 | Koninklijke Philips Electronics N.V. | Noise margin information for power control and link adaptation in IEEE 802.11h WLAN |
US20030048856A1 (en) * | 2001-05-17 | 2003-03-13 | Ketchum John W. | Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion |
US20030125040A1 (en) * | 2001-11-06 | 2003-07-03 | Walton Jay R. | Multiple-access multiple-input multiple-output (MIMO) communication system |
US20030129943A1 (en) * | 2001-12-18 | 2003-07-10 | Yunsang Park | Apparatus and method for link adaptation of packet data service on satellite systems |
US6611231B2 (en) * | 2001-04-27 | 2003-08-26 | Vivato, Inc. | Wireless packet switched communication systems and networks using adaptively steered antenna arrays |
US20040120411A1 (en) * | 2002-10-25 | 2004-06-24 | Walton Jay Rodney | Closed-loop rate control for a multi-channel communication system |
US20040157567A1 (en) * | 2003-02-10 | 2004-08-12 | Jittra Jootar | Weight prediction for closed-loop mode transmit diversity |
US20040171385A1 (en) * | 2001-07-03 | 2004-09-02 | Thomas Haustein | Adaptive signal processing method in a mimo-system |
US20050180369A1 (en) * | 2004-02-13 | 2005-08-18 | Hansen Christopher J. | Reduced latency concatenated reed solomon-convolutional coding for MIMO wireless LAN |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN1210888C (en) * | 2001-08-31 | 2005-07-13 | 连宇通信有限公司 | Method of transmitter diversity and transmitter diversity device |
US7184721B2 (en) * | 2003-10-06 | 2007-02-27 | Texas Instruments Incorporated | Transmit power control in a wireless communication device |
US7469491B2 (en) * | 2004-01-27 | 2008-12-30 | Crestcom, Inc. | Transmitter predistortion circuit and method therefor |
-
2006
- 2006-01-10 US US11/329,979 patent/US20070041322A1/en not_active Abandoned
- 2006-01-12 WO PCT/US2006/001244 patent/WO2006076583A2/en active Application Filing
- 2006-01-12 CN CN2006800019552A patent/CN101194467B/en not_active Expired - Fee Related
- 2006-01-12 TW TW095101284A patent/TWI406527B/en not_active IP Right Cessation
-
2015
- 2015-06-15 US US14/739,083 patent/US9936462B2/en not_active Expired - Fee Related
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6452348B1 (en) * | 1999-11-30 | 2002-09-17 | Sony Corporation | Robot control device, robot control method and storage medium |
US6611231B2 (en) * | 2001-04-27 | 2003-08-26 | Vivato, Inc. | Wireless packet switched communication systems and networks using adaptively steered antenna arrays |
US20030048856A1 (en) * | 2001-05-17 | 2003-03-13 | Ketchum John W. | Method and apparatus for processing data for transmission in a multi-channel communication system using selective channel inversion |
US20030022686A1 (en) * | 2001-06-29 | 2003-01-30 | Koninklijke Philips Electronics N.V. | Noise margin information for power control and link adaptation in IEEE 802.11h WLAN |
US20040171385A1 (en) * | 2001-07-03 | 2004-09-02 | Thomas Haustein | Adaptive signal processing method in a mimo-system |
US20030125040A1 (en) * | 2001-11-06 | 2003-07-03 | Walton Jay R. | Multiple-access multiple-input multiple-output (MIMO) communication system |
US20030129943A1 (en) * | 2001-12-18 | 2003-07-10 | Yunsang Park | Apparatus and method for link adaptation of packet data service on satellite systems |
US20040120411A1 (en) * | 2002-10-25 | 2004-06-24 | Walton Jay Rodney | Closed-loop rate control for a multi-channel communication system |
US20040157567A1 (en) * | 2003-02-10 | 2004-08-12 | Jittra Jootar | Weight prediction for closed-loop mode transmit diversity |
US20050180369A1 (en) * | 2004-02-13 | 2005-08-18 | Hansen Christopher J. | Reduced latency concatenated reed solomon-convolutional coding for MIMO wireless LAN |
Cited By (25)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090310590A1 (en) * | 2004-08-18 | 2009-12-17 | William Kish | Transmission and Reception Parameter Control |
US7890061B2 (en) * | 2006-06-27 | 2011-02-15 | Intel Corporation | Selective 40 MHz operation in 2.4 GHz band |
US20070298810A1 (en) * | 2006-06-27 | 2007-12-27 | Assaf Kasher | Selective 40 MHz Operation in 2.4 GHz Band |
US20090052319A1 (en) * | 2006-06-30 | 2009-02-26 | Alaa Muqattash | Reservation based mac protocol |
US8320244B2 (en) | 2006-06-30 | 2012-11-27 | Qualcomm Incorporated | Reservation based MAC protocol |
US20080167063A1 (en) * | 2007-01-05 | 2008-07-10 | Saishankar Nandagopalan | Interference mitigation mechanism to enable spatial reuse in uwb networks |
US8493955B2 (en) * | 2007-01-05 | 2013-07-23 | Qualcomm Incorporated | Interference mitigation mechanism to enable spatial reuse in UWB networks |
US20080225761A1 (en) * | 2007-03-13 | 2008-09-18 | Ning Zhang | Estimating Timing And Frequency Information For Multiple Channel Wireless Communication Systems |
US9344897B2 (en) * | 2007-03-13 | 2016-05-17 | Qualcomm Incorporated | Estimating timing and frequency information for multiple channel wireless communication systems |
US20090202014A1 (en) * | 2008-02-11 | 2009-08-13 | Syed Aon Mujtaba | Adaptation Techniques in MIMO |
US9154201B2 (en) | 2008-02-11 | 2015-10-06 | Intel Deutschland Gmbh | Adaptation techniques in MIMO |
US8855257B2 (en) | 2008-02-11 | 2014-10-07 | Intel Mobile Communications GmbH | Adaptation techniques in MIMO |
US9749023B2 (en) * | 2008-04-28 | 2017-08-29 | Apple Inc. | Apparatus and methods for transmission and reception of data in multi-antenna systems |
US8218690B1 (en) | 2008-09-29 | 2012-07-10 | Qualcomm Atheros, Inc. | Timing offset compensation for high throughput channel estimation |
US9124328B2 (en) | 2009-03-12 | 2015-09-01 | Futurewei Technologies, Inc. | System and method for channel information feedback in a wireless communications system |
US20100238913A1 (en) * | 2009-03-23 | 2010-09-23 | Futurewei Technologies, Inc. | Adaptive Precoding Codebooks for Wireless Communications |
US8675627B2 (en) | 2009-03-23 | 2014-03-18 | Futurewei Technologies, Inc. | Adaptive precoding codebooks for wireless communications |
US9124387B2 (en) * | 2013-01-23 | 2015-09-01 | Academia Sinica | Dynamic adaption of transmission rate for multiuser MIMO networks |
US20140204776A1 (en) * | 2013-01-23 | 2014-07-24 | Academia Sinica | Dynamic Adaption of Transmission Rate for Multiuser MIMO Networks |
DE102014208084A1 (en) * | 2014-04-29 | 2015-10-29 | Volkswagen Aktiengesellschaft | Estimate a reception probability of a data packet and a transmission rate for data packets |
US10069742B2 (en) | 2014-04-29 | 2018-09-04 | Volkswagen Ag | Estimating the probability that a data packet will be received and a data packet transmission rate |
US20160381701A1 (en) * | 2015-06-29 | 2016-12-29 | T-Mobile Usa, Inc. | Channel Coding for Real Time Wireless Traffic |
US10855597B2 (en) * | 2015-06-29 | 2020-12-01 | T-Mobile Usa, Inc. | Channel coding for real time wireless traffic |
US10771185B1 (en) | 2019-02-19 | 2020-09-08 | Samsung Electronics Co., Ltd. | System and method for setting link parameters in a WiFi link |
US11336388B2 (en) | 2019-02-19 | 2022-05-17 | Samsung Electronics Co., Ltd. | System and method for setting link parameters in a WiFi link |
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CN101194467A (en) | 2008-06-04 |
TW200635269A (en) | 2006-10-01 |
WO2006076583A2 (en) | 2006-07-20 |
TWI406527B (en) | 2013-08-21 |
WO2006076583A3 (en) | 2007-12-21 |
CN101194467B (en) | 2012-06-13 |
US20150282097A1 (en) | 2015-10-01 |
US9936462B2 (en) | 2018-04-03 |
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