ASYMMETRICAL FORWARD/REVERSE TRANSMISSION BANDWIDTH

Abstract

A wireless transceiver for use with a CDMA communication system is disclosed. The wireless transceiver comprises: a first sequence generator to provide a first sequence of values during a period, wherein the first sequence generator provides the first sequence of values repeatedly; a second sequence generator to provide a second sequence of values during the period and in alignment with the first sequence generator, wherein the second sequence generator provides the second sequence of values repeatedly; a first combiner to combine output signals of the first sequence generator and the second sequence generator to provide a third sequence of values during the period, wherein the first combiner provides the third sequence of values repeatedly; and a second combiner to combine an output signal from the first combiner with an input signal containing information; a radio front end to transmit an output signal from the second combiner to an antenna.

Claims

1. A wireless transceiver for use with a Code Division Multiple Access (CDMA) communication system, comprising: a first sequence generator to provide a first sequence of values during a period, wherein the first sequence generator provides the first sequence of values repeatedly; a second sequence generator to provide a second sequence of values during the period and in alignment with the first sequence generator, wherein the second sequence generator provides the second sequence of values repeatedly; a first combiner to combine output signals of the first sequence generator and the second sequence generator to provide a third sequence of values during the period, wherein the first combiner provides the third sequence of values repeatedly; a second combiner to combine an output signal from the first combiner with an input signal, the input signal containing information; and a radio front end to transmit an output signal from the second combiner to an antenna, wherein the first sequence of values is equivalent to a truncated version of a first PN code sequence, the second sequence of values is equivalent to a second PN code sequence, a length of the second PN code sequence is shorter than a length of the first PN code sequence, and a length of the truncated version of the first PN code sequence is equivalent to a length of the second sequence of values and a length of the third sequence of values.

2. The wireless transceiver of claim 1, wherein the second combiner is a spreader to encode the input signal with the output signal of the first combiner and wherein the input signal includes digital data.

3. The wireless transceiver of claim 2, wherein the wireless transceiver is included in a radio of a wireless transmit/receive unit (WTRU) that communicates with a base station.

4. The wireless transceiver of claim 1, wherein the second combiner is a despreader to decode the input signal with the output signal of the first combiner and wherein the input signal includes spread digital data.

5. The wireless transceiver of claim 4, wherein the wireless transceiver is included in a radio of a base station that communicates with a wireless transmit/receive unit (WTRU).

6. The wireless transceiver of claim 1, wherein the first sequence generator repeatedly provides the first sequence of values and the second sequence generator repeatedly provides the second sequence of values based on a timing event.

7. The wireless transceiver of claim 6, wherein the timing event is the expiration of a counter.

8. The wireless transceiver of claim 1, wherein the first sequence generator repeatedly reloads according to the period of the first sequence of values.

9. A wireless transceiver for use with a Code Division Multiple Access (CDMA) communication system, comprising: a first sequence generator capable of generating a first PN code sequence, the first sequence generator operable to repeatedly provide a first sequence of values with a period without generating all values of the first PN code sequence, the first sequence of values corresponding to a portion of the first PN code sequence; a second sequence generator to repeatedly provide a second sequence of values with the period; a first combiner to combine output signals of the first sequence generator and the second sequence generator to provide a third sequence of values with the period; a second combiner to combine an output signal from the first combiner with an input signal, the input signal containing information; and a radio front end to transmit an output signal from the second combiner to an antenna, wherein the second sequence of values is equivalent to a second PN code sequence, the second PN code sequence is shorter than the first PN code sequence, and the period of the first, second and third sequence of values is shorter than a period of the first PN code sequence.

10. The wireless transceiver of claim 9, wherein the second combiner is a spreader to encode the input signal with the output signal of the first combiner and wherein the input signal includes digital data.

11. The wireless transceiver of claim 10, wherein the wireless transceiver is included in a radio of a wireless transmit/receive unit (WTRU) that communicates with a base station.

12. The wireless transceiver of claim 9, wherein the second combiner is a despreader to decode the input signal with the output signal of the first combiner and wherein the input signal includes spread digital data.

13. The wireless transceiver of claim 12, wherein the wireless transceiver is included in a radio of a base station that communicates with a wireless transmit/receive unit (WTRU).

14. The wireless transceiver of claim 9, wherein the first sequence generator repeatedly provides the first sequence of values and the second sequence generator repeatedly provides the second sequence of values based on a timing event.

15. The wireless transceiver of claim 14, wherein the timing event is the expiration of a counter.

16. The wireless transceiver of claim 9, wherein the first sequence generator repeatedly reloads according to the period of the first sequence of values.

17. A wireless transceiver for use with a Code Division Multiple Access (CDMA) communication system, comprising: a first sequence generator to repeatedly provide a first sequence of values with a period, the first sequence of values corresponding to a portion of a first PN code sequence, the first sequence generator repeatedly providing the first sequence of values without generating all values of the first PN code sequence; a second sequence generator to repeatedly provide a second sequence of values with the period; a first combiner to combine output signals of the first sequence generator and the second sequence generator to provide a third sequence of values with the period; a second combiner to combine an output signal from the first combiner with an input signal, the input signal containing information; and a radio front end to transmit an output signal from the second combiner to an antenna, wherein the second sequence of values is equivalent to a second PN code sequence, the second PN code sequence is shorter than the first PN code sequence, and the period of the first, second and third sequence of values is shorter than a period of the long PN code sequence.

18. The wireless transceiver of claim 17, wherein the second combiner is a spreader to encode the input signal with the output signal of the first combiner and wherein the input signal includes digital data.

19. The wireless transceiver of claim 18, wherein the wireless transceiver is included in a radio of a wireless transmit/receive unit (WTRU) that communicates with a base station.

20. The wireless transceiver of claim 17, wherein the second combiner is a despreader to decode the input signal with the output signal of the first combiner and wherein the input signal includes spread digital data.

21. The wireless transceiver of claim 20, wherein the wireless transceiver is included in a radio of a base station that communicates with a wireless transmit/receive unit (WTRU).

22. The wireless transceiver of claim 17, wherein the first sequence generator repeatedly provides the first sequence of values and the second sequence generator repeatedly provides the second sequence of values based on a timing event.

23. The wireless transceiver of claim 22, wherein the timing event is the expiration of a counter.

24. The wireless transceiver of claim 17, wherein the first sequence generator repeatedly reloads according to the period of the first sequence of values.

25. A wireless transceiver for use with a Code Division Multiple Access (CDMA) communication system, comprising: a first sequence generator to repeatedly provide a first sequence of values, the first sequence of values having a first length; a second sequence generator to repeatedly provide a second sequence of values, the second sequence of values having a second length; a first combiner to combine output signals of the first sequence generator and the second sequence generator to provide a third sequence of values, the third sequence of values having a third length, wherein the first length, the second length and the third length are the same; a second combiner to combine an output signal from the first combiner with an input signal, the input signal containing information; and a radio front end to transmit an output signal from the second combiner to an antenna, wherein the first sequence of values is equivalent to a truncated version of a first PN code sequence, the second sequence of values is equivalent to a second PN code sequence, the second PN code sequence is shorter than the first PN code sequence, and each of the first, second and third lengths is shorter than a length of the first PN code sequence.

26. The wireless transceiver of claim 25, wherein the second combiner is a spreader to encode the input signal with the output signal of the first combiner and wherein the input signal includes digital data.

27. The wireless transceiver of claim 26, wherein the wireless transceiver is included in a radio of a wireless transmit/receive unit (WTRU) that communicates with a base station.

28. The wireless transceiver of claim 25, wherein the second combiner is a despreader to decode the input signal with the output signal of the first combiner and wherein the input signal includes spread digital data.

29. The wireless transceiver of claim 28, wherein the wireless transceiver is included in a radio of a base station that communicates with a wireless transmit/receive unit (WTRU).

30. The wireless transceiver of claim 25, wherein the first sequence generator repeatedly provides the first sequence of values and the second sequence generator repeatedly provides the second sequence of values based on a timing event.

31. The wireless transceiver of claim 30, wherein the timing event is the expiration of a counter.

32. A wireless transceiver for use with a Code Division Multiple Access (CDMA) communication system, comprising: a first sequence generator capable of generating a first PN code sequence, the first sequence generator operable to repeatedly provide a first sequence of values having a first length without generating all values of the first PN code sequence, the first sequence of values corresponding to a portion of the first PN code sequence; a second sequence generator to repeatedly provide a second sequence of values having a second length; a first combiner to combine output signals of the first sequence generator and the second sequence generator to provide a third sequence of values having a third length, wherein the first length, the second length and the third length are the same; a second combiner to combine an output signal from the first combiner with an input signal, the input signal containing information; and a radio front end to transmit an output signal from the second combiner to an antenna, wherein the second sequence of values is equivalent to a second PN code sequence, the second PN code sequence is shorter than the first PN code sequence, and each of the first, second and third lengths is shorter than a length of the first PN code sequence.

33. The wireless transceiver of claim 32, wherein the second combiner is a spreader to encode the input signal with the output signal of the first combiner and wherein the input signal includes digital data.

34. The wireless transceiver of claim 33, wherein the wireless transceiver is included in a radio of a wireless transmit/receive unit (WTRU) that communicates with a base station.

35. The wireless transceiver of claim 32, wherein the second combiner is a despreader to decode the input signal with the output signal of the first combiner and wherein the input signal includes spread digital data.

36. The wireless transceiver of claim 35, wherein the wireless transceiver is included in a radio of a base station that communicates with a wireless transmit/receive unit (WTRU).

37. The wireless transceiver of claim 32, wherein the first sequence generator repeatedly provides the first sequence of values and the second sequence generator repeatedly provides the second sequence of values based on a timing event.

38. The wireless transceiver of claim 37, wherein the timing event is the expiration of a counter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is an illustration of a prior art CDMA system.

[0014] FIG. 2 is a block diagram of a prior art pseudo-random code sequence generator.

[0015] FIG. 3 is a diagram of spreading code epochs for different bandwidth uplink and downlink in a prior art system.

[0016] FIG. 4 is a diagram of spreading code epochs for different bandwidth uplink and downlink in a prior art system.

[0017] FIG. 5 is a block diagram of a pseudo-random code sequence generator made in accordance with the present invention.

[0018] FIG. 6 is a block diagram of a base station made in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0019] The preferred embodiments will be described with reference to the drawing figures where like numerals represent like elements throughout.

[0020] The present invention allows communication in a CDMA system where the uplink and downlink bandwidths are of different size and are integer multiples of each other. The problem is illustrated in FIG. 3, where epoch starting point ambiguity results when the pseudo-random code sequence epoch of one side of the communication, for example the downlink 100, is shorter than that of the other side of the communication, for example the uplink 120. This problem is addressed by truncating the pseudo-random code sequence of the lower bandwidth side of the communication at the end of the epoch for the higher bandwidth side.

[0021] FIG. 4 shows epoch starting points for an uplink 420 and downlink 400, where the downlink clock-rate and bandwidth are twice those of the uplink. As shown, the starting points 422 and 424 for a complete uplink pseudo-random sequence 430 are aligned with every other starting point, 402 and 406 for a complete downlink pseudo-random sequence 410. In order to maintain alignment between starting points of every pseudo-random sequence, the present invention truncates the pseudo-random sequence for the lower bandwidth signal at the point where the higher repetition rate downlink sequence restarts 426. Hence, in the present invention, the communication side with the lower bandwidth and lower data rate produces a truncated pseudo-random sequence 428 that contains a fraction of the number of chips that are found in the full pseudo-random code sequence 430. In the example illustrated in FIG. 4, the ratio of downlink to uplink bandwidth is 2:1. Hence, the pseudo-random sequence for the uplink 428 would contain exactly one half the number of chips that are in the full sequence 430. Where the bandwidth ratio is 3:1, the lower bandwidth sequence would be one third of the full sequence, and so on for other bandwidth ratios.

[0022] Referring to FIG. 5, a pseudo-random sequence generator 500 is shown, which is capable of producing a truncated sequence in accordance with the present invention. The pseudo-random sequence generator 500 includes a data clock 502, a counter 508, a reset device 510 and two pseudo-random code generators 504, 506. As should be well recognized by those of skill in the art, the required number of clock cycles depends upon the communication side with the higher bandwidth. Accordingly, this count is input into the counter 508 via a count input line 512. The counter 508 is loaded to count the number of clock cycles output by the data clock 502. When the required number of clock cycles has elapsed, the counter 508 signals a reset device 510, which resets the two code generators 504, 506.

[0023] The pseudo-random sequence generated by generator 504 contains 233,415 chips. This sequence is evenly divisible by 3, 5, 7, 9, 13 and 19. The pseudo-random sequence generated by generator 506 contains 128 chips. This sequence is evenly divisible by multiples of 2, up to 128. Hence, the full pseudo-random sequence of 29,877,120 chips is evenly divisible by 2, 3, 4, 5 and other combinations of the factors of 128 and 233,415. For uplink/downlink bandwidth ratios that match these factors, precise truncation of the full sequence is possible. The present invention enables the low bandwidth side of the communication to complete its truncated pseudo-random epoch at the same time that the high bandwidth side is completing its epoch.

[0024] A base station 300 made in accordance with the present invention is shown in FIG. 6. The base station 300 includes a receiver section 302, a transmitter section 304 and a modem interface unit 318. The modem interface unit 318 provides an interface between the receiver and transmitter sections 302, 304 of the base station 300 and the user. The modem interface unit 318 has an architecture and clocking that makes it possible to read and write data at different rates. This is made possible by using different and adjustable clock speeds. Details of such designs are known to those skilled in the art.

[0025] An antenna 306 receives a signal from the subscriber unit, which is filtered by a band-pass filter 308. The output of the filter 308 is downconverted by a mixer 310 to a baseband signal using a constant frequency (Fc) local oscillator. The output of the mixer 310 is then spread spectrum decoded at each modem by applying a pseudo-random sequence to a mixer 312 within the pseudo-random Rx sequence generator 314. The output of the mixer 312 is then forwarded to the modem interface unit 318.

[0026] For transmission, a baseband signal is received from the modem interface unit 318. Preferably, a 32 kb/s ADPCM signal is used. The ADPCM or PCM signal is applied to a mixer 322 within the pseudo-random Tx sequence generator 324. The mixer 322 multiplies the ADPCM or PCM data signal with the pseudo-random Tx sequence. The output of the mixer 322 is applied to low-pass filter 326. The output of the filter 326 is then applied to a mixer 328 and suitably up-converted. The up-converted signal is then passed through a band-pass filter 330 and to a broadband RF amplifier 332 which drives an antenna 334. Although two antennas 306, 334 are shown, the preferred embodiment includes a diplexer and only one antenna for transmission and reception.

[0027] The digital signal processor (DSP) 336 controls the acquisition process as well as the pseudo-random Rx and Tx sequence generators 314, 324. In accordance with the present invention, the pseudo-random Rx and Tx sequence generators 314, 324 are clocked separately and independently by the DSP 336. Accordingly, the data clocks (not shown) for the pseudo-random Rx and Tx sequence generators 314, 324 are separate and independent.

[0028] For a link to be established, both the base station 300 and subscriber unit must know what chip rates are used for uplink 120 and downlink 100. This information may be exchanged between the base station 300 and the subscriber unit by sending each other messages containing this information at the time of every call establishment. Or, alternatively, this information, including chip rates used for uplink 120 and downlink 100 transmissions, may be a system parameter that is programmed into the subscriber unit and the base station 300.

[0029] Although the invention has been described in part by making detailed reference to certain specific embodiments, such details is intended to be instructive rather than restrictive. It will be appreciated by those skilled in the art that many variations may be made in the structure and mode of operation without departing from the spirit and scope of the invention as disclosed in the teachings herein.