Asymmetrical forward/reverse transmission bandwidth

Asymmetric forward/reverse transmission bandwidth

The first figure shows an example diagram of CDMA;

The second figure shows a block diagram of a random code sequence generator with conventional techniques;

The third figure shows a block diagram of a distributed coding period for uplink and downlink of different bandwidths of a conventional technique;

The fourth figure shows a block diagram of a distributed coding period for uplink and downlink of different bandwidths of a conventional technique;

The fifth figure shows a block diagram of a dummy random code distribution generator made according to the present invention;

Figure 6 shows a block diagram of a base station made according to the present invention.

The present invention relates to a wireless digital communication system. More specifically, the present invention relates to a code-division multiple access (CDMA) communication system where a user unit and a base station use different bandwidths to communicate with each other.

The CDMA system provides an efficient use of the limited bandwidth of the RF spectrum, thereby allowing a larger amount of information transmission and is more effective than communication systems using other technologies, such as time division multiple access and frequency division multiple access. Less signal distortion.

In a CDMA communication system, an information signal on the transmitter is mixed with a dummy randomly distributed code that distributes the information across the entire bandwidth used by the system. This distributed signal is upscaled and converted into a radio frequency (RF) signal for transmission. A receiver is identified by the same dummy random code, and the transmitted distributed spectrum signal is down-converted and mixed with the down-converted signal to be used to distribute the original information signal so that it regenerates the original information signal The same dummy is freely coded.

A conventional CDMA communication system is shown in the first figure. This communication system has a plurality of base stations 20 ₁ ,20 ₂ ,…20 _n The public switched telephone network (PSTN) that passes through an area is connected by land lines or by a wireless connection. Any base station 20 ₁ ,20 ₂ ,…20 _n Use distributed spectrum CDMA transmission to communicate with mobile or field user unit stations located in its cell area 22 ₁ ,22 ₂ ,…22 _n Communication.

In a typical CDMA system using technology, the downlink bandwidth used by the base station for transmission to the user unit is the same as the uplink bandwidth used by the user unit for transmission to the base station. When the data capacity of the upper link and the lower link are roughly the same, the symmetrical configuration of the bandwidth is appropriate, as in the case of voice communication. However, in some communication schemes, the configuration of the peer-to-peer bandwidth for uplink and downlink transmission is an inefficient use of the limited radio frequency spectrum available to a wireless communication provider. For example, personal use of the Internet generally only transmits limited data, which may include network addresses, search items, and keyboard responses to inquiries. In contrast, an Internet server generally responds to a user's request and allows the user to receive a large amount of text, graphics, and other forms of data. In this case, providing a larger downlink bandwidth for transmitting the connection from the base station to the user unit and a smaller uplink bandwidth for transmitting the connection from the user to the base station allows configuration The entire bandwidth for communication providers is used more efficiently. Although it is the use of an asymmetrical bandwidth communication where the upper and lower bandwidths are the same as the full bandwidth, in an asymmetrical communication, the higher-used downlink channel can be connected by A larger bandwidth without sacrificing the performance of transmitting an uplink channel with a limited amount of data at a very low transmission rate can transmit data more quickly.

In a typical conventional CDMA system, a user unit generates a dummy randomly distributed sequence. This sequence is repeated every 29,877,120 clock cycle. In this technology, the complete sequence is recognized in a specific epoch. A conventional technique system 200 is used to generate a dummy random sequence as shown in the second figure. A data clock 202 is input to a first code generator 204 used to generate a dummy random sequence of 233,415 units (chips), and is also input to a first code generator 204 used to generate a dummy random sequence of 128 units (chips) A second code generator 206. The outputs of these two generators are combined to produce a dummy random sequence of 233,415×128, which has a total length of 29,877,120 units. At the end of the sequence, the code generator 204, 206 restarts the code from the beginning of the sequence.

When a user unit first starts to transmit, its dummy random sequence is free to operate. Its time is not synchronized with the time period when this pseudo random sequence starts when the base station is generated. Therefore, the base station must search for the beginning of the random code of the user unit, which is a time-consuming process.

In a conventional technique as described above, in terms of the upper link and the lower link, a dummy random distribution sequence is used to lock to devices of different bandwidths with different data rates. The third figure shows the starting point of the time period for the upper link 120 and the lower link 100, where the lower link clock rate is twice that of the upper link. As shown, the starting points of the upper connecting period, 122 and 124, are aligned with the starting points of each lower connecting period, 102 and 106. This creates ambiguity in the user unit. When trying to decode the downstream data, the duration of the downstream connection will not be noticed. For downlink transmission, it starts at 122 at the beginning of the uplink period, and the downlink start point can be 102 or 104. This ambiguity caused the user unit to search the entire sequence to find this starting point. This process consumes an unacceptably long time, and therefore produces an unrealistic use of the non-compliance bandwidth.

Therefore, in the case of the CDMA system, when the uplink bandwidth is different from the downlink bandwidth, here it is necessary to keep the dummy and random distributed codes of the uplink and the downlink synchronized.

The present invention is to promote CDMA communication in which the transmission bandwidth of the uplink and the downlink are not at the same time. When there is a disproportionate amount of information transmission between the upstream and downstream channels, the asymmetrical configuration of the transmission bandwidth is advantageous. In this system, the higher bandwidth must be an integer multiple of the lower bandwidth. This system includes a base station and a user unit, each of which has two dummy and arbitrary code generators that can be set separately to become two independent data clocks, and one can use different A modem interface with data rates to read and write. The alignment of the up-link and the down-link imaginary distributed codes can be achieved by truncating the slower distributed code sequence at the end of a complete code sequence connected at a higher rate.

The purpose and advantages of the present invention will be more apparent after reading the detailed description of the preferred specific embodiments mentioned herein.

Schematic description

The first figure shows an example diagram of CDMA;

The second figure shows a block diagram of a random code sequence generator with conventional techniques;

The third figure shows a block diagram of a distributed coding period for uplink and downlink of different bandwidths of a conventional technique;

The fourth figure shows a block diagram of a distributed coding period for uplink and downlink of different bandwidths of a conventional technique;

The fifth figure shows a block diagram of a dummy random code distribution generator made according to the present invention;

Figure 6 shows a block diagram of a base station made according to the present invention.

This preferred embodiment will be described in detail by referring to the drawings, where the same numbers from the beginning to the end will indicate the same elements.

The present invention permits communication in a CDMA system, and the bandwidth of the upper link and the lower link can be different and have an integer multiple of each other. Just like the problem mentioned in the third figure, when the dummy random code sequence period on the side of the communication is at the beginning of this period, the result will be blurred. The length of the side, for example, the upper link 120. This problem is handled by truncating the dummy random sequence on the lower bandwidth side of the communication at the time terminal on the higher bandwidth side.

The fourth diagram shows the starting point of a time period of the upper link 420 and the lower link 400, where the clock rate and bandwidth of the lower link are twice that of the upper link. As shown, the starting points 422 and 424 of a complete uplink dummy random sequence 430 are aligned with each of the starting points 402 and 406 of a complete downlink dummy random sequence 410. In order to maintain the alignment between the starting points of each dummy arbitrary sequence, the present invention truncates the dummy arbitrary sequence of the lower bandwidth sequence number at the time point 426 at the beginning of the lower sequence of the higher repetition rate. Therefore, in the present invention, the communication side with lower bandwidth and lower data rate generates a truncated dummy random sequence 428, which includes those that can be found in this completely dummy random code sequence 430 Part of the number of units. In the example in the fourth figure, the bandwidth ratio of the lower link to the upper link is 2:1. Therefore, the imaginary random sequence used for the uplink 428 will contain exactly half of the number of such units in the complete sequence 430. Here the bandwidth ratio is 3:1, this lower bandwidth sequence will be one-third of the full sequence, and the same is true for other bandwidth ratios.

Please refer to the fifth figure, which shows a dummy random sequence generator 500, which can generate a truncated dummy column according to the present invention. The dummy random sequence generator 500 includes a data clock 502, a counter 508, a reset element 510, and two dummy random code generators 504 and 506. As will be understood by those who are familiar with these skills, the number of clock cycles required here depends on the communication side with higher bandwidth. Therefore, the count is input to the counter 508 via a count input line 512. The counter 508 is used 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 sends a signal to reset the component 510, and it resets the two code generators 504, 506.

This dummy random code is generated by the generator 504 containing 223,415 units. This sequence can be divided evenly by 3, 5, 7, 9, 13, and 19. This imaginary random sequence is generated by a generator 506 containing 128 units. This sequence can be divisible by integers from 2 to 128. Therefore, this complete imaginary random sequence of 29,887,120 units can be divided by other combinations of factors of 2, 3, 4, 5 and 128 and 223,415. For up-link/down-link bandwidth ratios that meet these factors, this complete sequence may be uniformly truncated. The present invention enables the low-frequency side of this communication to achieve its truncated imaginary random period at the same time as the period of its completion on the high-frequency side.

As shown in Fig. 6 is a base station 300 made according to the present invention. The base station 300 includes a receiving station 302, a transmitting station 304, and a modem interface unit 318. The modem interface unit 318 provides an interface between the receiving station and the transmitting station 302, 304 of the base station 300 and the user. The modem interface unit 318 has an architecture and clock so that it can read and write materials at different rates. This makes it possible to use different and adjustable clock rates. The details of these designs are well known to those who are familiar with these skills.

An antenna 306 receives the signal from the user unit, and the signal is filtered by a band pass filter 308. The output of the filter 308 is down-converted into a baseband signal by a mixer 310 and a fixed frequency (Fc) area oscillator. The output of the mixer 310 is distributed spectrum decoded on any modem by applying a dummy random sequence to a mixer 312 in the dummy random Rx sequence generator 314. The output of the mixer 312 is then forwarded to the modem interface unit 318.

For transmission, a baseband signal is received at the modem interface unit 318. Preferably, a 32kb/s ADPCM signal is used. The ADPCM or PCM signal is applied to the mixer 322 in the dummy Tx sequence generator 324. The mixer 322 multiplexes the ADPCM or PCM data signal with the dummy Tx sequence. The output of the mixer 322 is applied to the low-pass filter 326. The output of this filter 326 is then applied to a mixer 328 and up-converted appropriately. The up-converted signal passes through a band-pass filter 330 and goes to a broadband RF amplifier 322 for driving an antenna 334. Although, as shown, there are two antennas 306, 334, but the preferred embodiment includes a co-duplex antenna for transmission and reception.

The digital signal processor (DSP) 336 controls the data collection process and dummy Rx and Tx sequence generators 314, 324. According to the present invention, the dummy Rx and Tx sequence generators 314, 324 are separated and independent.

For the connection to be established, both the base station 300 and the user unit must know the unit rate for the uplink 120 and the downlink 100. This message can be exchanged between the base station 300 and the user unit by sending messages containing this information to each other at the moment when each paging is established. Or, in addition, the message including the unit rate used in the uplink 120 and the downlink 100 transmission can also be a system parameter planned for the user unit and the base station 300.

Although the present invention has been described with detailed reference to specific specific embodiments, these details are used to illustrate the present invention but do not limit the present invention to this specific example. Those who are familiar with these techniques know that the various changes in the structure or the operation form resulting therefrom are inseparable, just as the spirit and scope of the present invention are disclosed in this technology.

Schematic description

100, 400. . . Next link

102, 106, 122, 124, 402, 406, 422, 424. . . Starting point

120, 420. . . Shanglian

200. . . Skill System for Practice

202, 502. . . Material clock

204. . . First code generator

206. . . Second code generator

300. . . Base station

302. . . Receiving station

304. . . Transmission station

306, 334. . . antenna

308, 330. . . Band pass filter

310, 312, 322, 328. . . Mixer

314. . . Rx sequence generator

318. . . Modem Interface Unit

322. . . Broadband RF amplifier

324. . . Tx sequence generator

326. . . Low pass filter

336. . . Digital signal processor

410. . . Follow a dummy arbitrary sequence

426. . . Start of next sequence

428. . . Truncated fictitious random sequence

430. . . Uplink Fictitious Random Sequence

500. . . Fictitious random sequence generator

504, 506. . . Code generator

508. . . counter

510. . . Reset component

512. . . Counting input line