WO2004006458A1

WO2004006458A1 - Data communication method using pn code on wireless telemetry system

Info

Publication number: WO2004006458A1
Application number: PCT/KR2002/001089
Authority: WO
Inventors: Seong-Joo Lee; Kyung-Duk Kim; Jae-Seok Kim; Gun-Hee Han
Original assignee: Zethos Co., Ltd.
Priority date: 2002-05-28
Filing date: 2002-06-10
Publication date: 2004-01-15
Also published as: AU2002303032A1; KR20030091434A

Abstract

Disclosed is a data communication method using PN(pseudo-noise) code on a wireless telemetry system, in which a control unit wirelessly calls a plurality of remote terminals that are scattered in places, and the plurality of remote terminals, as a respondent, transmit measured data based on the PN code by a spread-spectrum communication method. Multiple access method through a PN code sharing method according to the present invention has the advantage that can overcome capacity limit due to a number of PN codes in the existing CDMA system. Also, the only remote terminal that is called by a central unit transmits data, and therefore it can minimize complexity of a system because complicated protocol or call processing is not needed.

Description

DATA COMMUNICATION METHOD USING PN CODE ON WIRELESS

TELEMETRY SYSTEM

Technical Field

The present invention relates to a data communication method using a

PN(psuedo-noise) code on a wireless telemetry system, in which a control unit wirelessly calls a plurality of remote terminals that are scattered in places, and the plurality of remote terminals, as a respondent, transmit measured data based on the PN code by a spread-spectrum communication method.

Background Art

A spread-spectrum communication is a method that spreads the spectrum of the information data signal into a code (e.g., PN code or walsh code) having much wider spectrum than the frequency bandwidth of the information data. In the method, the code is independent of the information data signal, and a receiver recovers the original information data by contracting the spectrum of the transmitted signal, using a synchronous code ever used by a transmitter. Giving different codes to users using spread-spectrum communication is called a code division multiple access, "CDMA" . In CDMA, a plurality of users are capable of transmitting the data at the same time and on the same frequency, by using PN codes. On the other hand, in a system designed for a mobile telephone service, such as IS-95 etc., whenever a certain user requests to initiate commumcation, a PN code is assigned to the requester. Therefore, it is impossible to assign a PN code to a certain terminal whenever the terminal wants. Furthermore, in conventional mobile phone services, since most of the users irregularly request for communication, a base station must manage PN codes for multiple access, and a very complicated call processing is need to process calls of the plurality of users. Under these kinds of system, it is impossible for many terminals to share a particular PN code.

A wireless telemetry system is comprised of a central processing unit, CU, and a plurality of remote terminals, RT, in which the data measured by RTs are wirelessly transmitted to CU. In this kind of wireless telemetry system, unlike the conventional CDMA technology, CU does not need a number of PN codes because CU is able to directly control data transmission time of all RTs by using wireless remote call. However, since a wireless telemetry system must accommodate a number of RTs quite simply structured, it is difficult to adopt the conventional CDMA technology to the wireless telemetry system. For these reasons, a new communication method applicable to a wireless telemetry system is needed.

Disclosure of Invention

This invention has been invented to answer the purpose of developing new communication method in a wireless telemetry system. Therefore, it is an object of the present invention to provide a data communication method using a PN(psuedo-noise) code on a wireless telemetry system, characterized in that, when a single CU communicates with the plurality of RTs, the limited numbers of RTs are used, so that more RTs can transmit data.

To achieve the above object, there is provided a data communication method using a PN(psuedo-noise) code on a wireless telemetry system, which comprises a control unit, CU, and a plurality of remote terminals, RTs, the method comprising the step of the CU's calling one of the RTs, and only the called RT's transmitting data, by using a single PN code.

According to another feature of the present invention, there is provided a data communication method using a PN(psuedo-noise) code on a wireless telemetry system which comprises a control unit, CU, and a plurality of remote terminals, RTs, the method comprising the step of: the CU's calling the plurality of RTs, and the called

RTs' transmitting data by using an assigned PN codes.

In the above, the PN codes that the respective RTs use for transmitting data is prescribed by the following equations: [Equation 1]

PN code number = the upper m-bit of the RT number [Equation 2] n=log₂(the number of PN code) As yet another feature of the present invention, there is provided a. data communication method using a PN(psuedo-noise) code on a wireless telemetry system which comprises a control unit, CU, and a plurality of remote terminals, RTs, the method comprising the step of: the CU's assigning a wait factor to the respective RTs, and calling the RTs simultaneously, and the called RTs' transmitting data after transmission time determined by the wait factor, using the same PN code.

FIG. 1 shows a data flow between CU and RTs. If a DB(database) server 10 calls i-th RT (SI), a CU modem 13 transmits data to an RT modem 15 through an RT call channel 4 (S2). Then, the RT modem 15 demodulates the RT call channel in order to check whether or not the RT is called, and if the RT was called, the RT modem 15 receives and stores the measurement data from a measuring device 17 (S3). The RT modem 15 transmits the measurement data to the CU modem 13 through a data channel (S4), and the CU modem 13 demodulates the data channel in order to recover the measurement data from the RT modem 15 and transmits the recovered measurement data to the DB server 10 (S5).

Brief Description of Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a system configuration of the present invention, FIG. 2 is a conceptual view showing a first embodiment of the present invention, FIG. 3 is a conceptual view showing a second embodiment of the present invention, FIG. 4 is a conceptual view showing a third embodiment of the present invention,

FIGs. 5 to 7 are brief configurations of a transmission channel created when CU calls RTs,

FIG. 8 is a brief configuration of a transmission channel transmitted from RT to CU, and FIG. 9 is a diagram showing a protocol between CU and RTs.

Preferred Embodiments for Carrying out the Invention

A preferred embodiments will be described herein below with reference to the accompanying drawings. First Embodiment

In this embodiment, CU and RTs commumcate with each other using a single

PN code. Since CU calls RT intermittently and the called RT only transmits the PN code-based data, the present embodiment does not require a number of PN codes and is able to communicate with a single PN code, unlike the commonly used CDMA method.

FIG. 2 shows how CU calls RTs and how the called RTs transmit data to CU. In FIG. 2, if CU calls z^'-th RT, RT; (2), the z^'-th RT demodulates the RT call channel to recognize that it was called and then transmits measurement data to CU (3). The delay time, T_delay (4), taken from when RT,- receives CU's call to when RT,- starts transmitting the measurement data, varies according to the distance between CU and RT. Therefore, the RT_;'s enable time, T,- (5), taken from when CU calls RT; to when RT,- finishes transmitting the data, also varies according to the respective RTs, rather than is constant. After RT, call process is done, CU calls the nexty^'-th RT, RT (6), to perform the same process as was done on RT_;. If there is no reply to the call for a certain time, CU deems that the relevant RT has failure to communication, and it may recall the relevant RT or the next RT.

As shown in FIG. 2, CU may call RT either serially from first one to N-th one or randomly, at CU's convenience. Alternatively, CU may call all of the RTs one time periodically, or, may call a certain RT repeatedly.

Second Embodiment

This embodiment is about giving a transmission delay to each the RTs, when CU calls RTs, so that a plurality of RTs may share a single PN code. FIG. 3 is a timing diagram showing that CU calls four RTs and the called RTs share a single PN code, in the case of using a wait factor and of the frame period of a data channel is 20msec.

As shown in FIG. 3, CU serially calls four RTs, B,-, R,, R_k, R_m, through an RT call channel (1) and allots different wait factors, WF, to the respective RTs (2). Then, each the called four RTs transmits data after its wait time. E.g., the z^'-th RT transmits data after zero(0) msec from RT call occurrence (3) , they^'-th RT transmits data after 90 msec from RT call occurrence (4), the k-t RT transmits data after 30 msec from RT call occurrence (5), the m-th RT transmits data after 60 msec from RT call occurrence (6), by sharing a single PN code. If there is no reply to the call for a certain time, CU deems that the relevant RT has failure to commumcation, and it may recall the relevant RT or the next RT.

Third Embodiment

This embodiment is about data communication using a plurality of PN codes on a wireless telemetry system. FIG. 4 is a brief timing diagram showing a way to call four RT in a wireless telemetry system capable of operating four PN codes.

As shown in FIG. 4, if CU serially calls four RTs, R,, R_/5 R_k, R_m, through an RT call channel (1), each the called four RTs transmits data using the relevant PN codes. For example, the z^'-th RT transmits data, using 0-th PN code (2); fhey^'-th RT transmits data, using a first PN code (3); the k-ύι RT transmits data, using a second PN code (4); and the m-th RT transmits data, using a third PN code (5). Since the delay time taken by the four RTs' data transmission is different to each other, a call for z^'-th transmission group, SG,-, is finished at the time of keeping up with the data of m-th RT that arrives last. If there is no reply to the call for a certain time, CU deems that the relevant RT has failure to communication, and it shifts into the next transmission group SG_y (7).

In FIG. 4, the PN codes that the respective RTs use for transmitting data is prescribed by the number of each RTs. The method of determining data transmission time by using RT number is represented by the Equations 3 and 4. [Equation 3]

PN code number = the upper n-bit of the RT number [Equation 4] n=log₂(the number of PN code) For example, in the case that maximum 16 PN codes are available in a wireless telemetry system, the upper 4 bits (n=log₂16=4) of the RT number is the PN code number. Suppose that CU calls 1033rd (in binary, 10000001001) RT and 1162nd (in binary, 10010001010) RT at the same time. Since the upper four bits of RT number of the 1033rd RT is "1000" and the upper four bits of RT number of the 1162nd RT is "1001", an 8th PN code and a 9th PN code are used to transmit data to CU. Here, since the 1033rd RT and the 1162nd RT use the different PN codes, simultaneous transmission becomes possible.

The PN code numbers that RTs use for transmitting data may not be fixed to RT numbers, and instead, the PN code number may be assigned to the respective RTs, in need of CU. In this case, the configuration of an RT call channel becomes different. More detailed description about this follows:

Channel configuration

FIG. 5 shows a brief configuration of a channel transmitted by CU to call RTs. CU transmits a pilot channel (1) to all the RTs. The pilot channel helps that the respective RT smoothly carries out synchronization against a PN code transmitted by CU, and at the same time, performs synchronous demodulation of the RT call channel (2) sent from CU. The RT call channel (2) plays a role of transmission channel for the RT numbers. The RT call channel is composed of total 16 bits, and in it the lower 5 bits are a frame quality indication bits for checking the transmission frame error. The pilot channel (1) is a channel that is always transmitted, and the RT call channel (2) is a channel that is transmitted only when a particular RT is called.

FIG. 6 shows a brief configuration of a channel transmitted by CU to variably assign PN code numbers to RTs. CU transmits a pilot channel (1) to all the RTs. The pilot channel (1) helps that the respective RT smoothly carries out synchronization against a PN code transmitted by CU, and at the same time, performs synchronous demodulation of the RT call channel (2) sent from CU. The RT call channel (2) plays a role of transmission channel for the RT numbers. The RT call channel is comprised of total 32 bits, and in it the upper 10 bits direct the called RT numbers (3). The next 4 bits direct the PN code number (4) that the called RT will use, and the next 8 bits are control data (5) for CU to control RT. The lowest 10 bits are a frame quality indication bits (6) for checking the transmission frame error. The pilot channel (1) is a channel that is always transmitted, and the RT call channel (2) is a channel that is transmitted only when a particular RT is called.

FIG. 7 shows a brief configuration of a channel to which a wait factor is added, so that a plurality of RTs may share a single PN code. CU transmits a pilot channel (1) to all the RTs. The pilot channel (1) helps that the respective RT smoothly carries out synchronization against a PN code transmitted by CU, and at the same time, performs synchronous demodulation of the RT call channel (2) sent from CU. The RT call channel (2) plays a role of transmission channel for the RT numbers. The RT call channel is comprised of total 32 bits, and in it the upper 10 bits direct the called RT numbers (3). The next 4 bits represent a wait factor (4) that determines transmission delay from when RT is called to when the RT sends data, and the next 8 bits are control data (5) for CU to control RT. The lowest 10 bits are a frame quality indication bits (6) for checking the transmission frame error. The pilot channel (1) is a channel that is always transmitted, and the RT call channel (2) is a channel that is transmitted only when a particular RT is called. In FIG. 7, a wait factor (4) is comprised of. 4 bits, and these 4 bits combinationally direct a variety of transmission delay. The wait time or delay time from being called to transmission is determined by Equation 5. [Equation 5]

Transmission delay = wait factor x frame period of data channel x 1.5 For example, in the case that the frame period of a data channel is 20 msec, the wait factor of a first RT is

the first RT transmits data after 330 msec from being called and the second RT transmits data after 300 msec from being called. Therefore, although the first and the second RTs use a single PN code, the data transmission conflict can be avoided. In Equation 5, the multiplier "1.5" is a margin factor for compensating for transmission delay and/or processing delay between CU and RT. In FIG. 7, since a wait factor is comprised of 4 bits, maximum 16 RTs can simultaneously be called.

FIG. 8 shows a configuration of a data channel to be used for transmitting data from RT to CU. As shown, the respective RTs use the data channel to transmit measurement data to CU. The data channel includes a preamble (1), a fame sync FS (2), a pilot symbol P (3), and a measurement information (4). The preamble (1) is a data for CU to synchronize the PN codes sent from RT. The frame sync (2) is a symbol data for synchronizing the frame sent from RT. The pilot symbol (3) estimates a channel, and the measurement data (4) means a data obtained from sensors of RT. The measurement data (4) is channel-coded so that errors, which may be occurred while the data is transmitted in air, can be corrected. N- RTs do not use their unique PN codes, and instead, they use the same PN code to spread a data channel.

FIG. 9 is a diagram showing a protocol relation between CU and RTs according to the first embodiment of the present invention. First, if z^'-th RT, RT,-, is initially booted on the wireless telemetry system (Sll), the RT, synchronizes the PN code using a pilot channel sent from CU (SI 3). After PN code synchronization, RT_; demodulates the RT call channel sent from CU to await being called from CU (SI 5). In the mean time, if the RT,- is called, it transmits measurement data got from the sensors to CU (SI 6), and continues demodulating the RT call channel to await being called (SI 8). CU demodulates the received data to check whether or not there is errors on the demodulated data (S17). If no errors, CU calls the nexty^'-th RT; if errors are founded, CU may recall the previous relevant RT, i.e., RT;.

From the foregoing, the data communication method of the present invention can overcome the capacity restriction of a conventional CDMA system due to a number of PN codes. Moreover, since the present invention uses quite simple algorithm that only RT called by CU transmits data, an overall system becomes simpler and economic. This invention is especially useful in a wireless telemetry system that a number of RTs must transmit data frequently and at a low speed. While the invention has been shown and described with reference to a certain embodiment to carry out this invention, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

What Is Claimed Is:

1. A data communication method using a PN(psuedo-noise) code on a wireless telemetry system which comprises a control unit, CU, and a plurality of remote terminals, RTs, the method comprising the step of: the CU's calling one of the RTs, only the called RT's transmitting data, by using a single PN code.

2. The method of claim 1, wherein the CU generates an RT call channel for calling one of the RTs; wherein the RT demodulates the RT call channel to await being called from the

CU, and if it is called, it transmits data.

3. The method of claim 1, wherein, if there are errors on the data transmitted from the called RT, the CU recalls the RT.

4. The method of claim 1, wherein the CU calls the RT at random or in regular order.

5. A data communication method using a PN(psuedo-noise) code on a wireless telemetry system which comprises a control unit, CU, and a plurality of remote terminals, RTs, the method comprising the step of: the CU's calling the plurality of RTs, the called RTs' transmitting data by using an assigned PN codes.

6. The method of claim 5, wherein the PN codes that the respective RTs use for transmitting data is prescribed by the following equations:

PN code number = the upper m-bit of the RT number n=log₂(the number of PN code)

7. The method of claim 5, wherein the PN codes that the respective RTs will use are assigned by an RT call channel created when the CU calls the RTs.

8. The method of claim 7, wherein the RT call channel comprises an RT number, a

PN code, and a control data.

9. A data communication method using a PN(psuedo-noise) code on a wireless telemetry system which comprises a control unit, CU, and a plurality of remote terminals, RTs, the method comprising the step of: the CU's assigning a wait factor to the respective RTs, and calling the RTs simultaneously, and the called RTs' transmitting data after transmission time determined by the wait factor, using the same PN code.

10. The method of claim 9, wherein the transmission delay is determined by the following equation: transmission delay = wait factor x wait factor x frame period of data channel x 1.5.

11. The method according to one of claims 1 to 10, wherein the data channel transmitted from the RT to the CU comprises: a preamble for synchronizing the PN codes sent from RT, a frame sync for synchronizing the frame sent from RT, a pilot symbol for estimating a channel, and a measurement data.

12. The method according to one of claims 1 to 10, wherein if there are errors on the data that the CU received from the RT, the CU recalls the relevant RT, or call the next RT.

13. The method according to one of claims 1 to 10, wherein if the called RT does not transmit data during a prescribed time, the CU recalls the relevant RT, or call the next RT.