CN1744463A - Up closed ring synchronous control method in time division-synchronous CDMA accessing system - Google Patents

Abstract

The method is applicable to TD-SCDMA system. In procedure for controlling up-going closed loop power, after receiving up-going signal from user device, node B measures and calculates impulse response at monitored position, and compares it with target position so as to generate command of synchronization adjustment. Leading in correlation coefficient of transmission characteristic of wireless channel, the method calculates correlativity of transmission characteristic of wireless channel in two adjacent up-going cycles n, n-1 so as to obtain change of impulse response in wireless channel. Thus, weight values of maximum peak value and average maximum peak value of impulse response in wireless channel in current up going close synchronization control cycle can be self-adaptive adjusted. The invention improves performance under different transmission characteristics of wireless channel in procedure of up going close synchronization control.

Description

Up closed loop synchronisation control means in the time-division-synchronous CDMA access system

Technical field

The present invention relates to physical layer (Physical Layer or the Layer 1) control method in a kind of wireless communication system, more specifically to up closed loop Synchronization Control (the Uplink Close Loop Synchronization Control) method in Time Division-Synchronous Code Division Multiple Access access (Time Division-Synchronous Code Division MultipleAccess) system, can be according to the variation of wireless channel transmission characteristic, adaptive the closed loop synchronisation control means is adjusted, thereby improved the performance of up closed loop Synchronization Control process.

Background technology

In the TD-SCDMA 3-G (Generation Three mobile communication system), up link (Uplink) adopts the mode of time division duplex (Time Division Duplex) to be separated with down link (Downlink), be up link and down link and go up the ascending time slot (Uplink timeslot) and descending time slot (Downlink timeslot) of non-overlapping copies respectively setup time, make the transmission of Node B (Node B) and subscriber equipment (User Equipment) and be received on the mutually different time and carry out.Time division duplex is compared with Frequency Division Duplexing (FDD) (Frequency Division Duplex) mode, because under time division duplex, the uplink and downlink link uses identical frequency range, Node B and subscriber equipment all only need a cover radio circuit, thereby the cost of system can be greatly diminished, and because under time division duplex, the number of time slot that keep supplying, down link uses can flexible configuration, thereby realize the transmission of uplink and downlink link different rates, thereby can realize the symmetry or the asymmetric transmission of uplink and downlink link easily.

When time division duplex has above-mentioned advantage, time division duplex also produces some distinctive demands for the TD-SCDMA 3-G (Generation Three mobile communication system), wherein, in a sub-district of described system, do not disturb mutually for the transmission that makes each subscriber equipment in the sub-district with between receiving, need in the sub-district, to set up uplink synchronisation between each subscriber equipment and sub-district Node B, make the transmission signal of each subscriber equipment in the sub-district in the time of setting, arrive the sub-district Node B simultaneously: after the subscriber equipment start (Power on) in described sub-district, described subscriber equipment is by detecting the down-going synchronous physical channel (DwPCH) in the descending pilot frequency time slot (DwPTS), search for the sub-district at its place, and the downlink synchronization between foundation and its sub-district, place Node B; Then, described subscriber equipment is by its down-going synchronous physical channel that receives, estimate uplink synchronous physical channel (UpPCH) transmitting time roughly and required transmitted power, in uplink pilot time slot (UpPTS), send the uplink synchronous physical channel to described Node B, described Node B is according to the time of reception of uplink synchronous physical channel in the uplink pilot time slot, generation is to the adjustment instruction of described subscriber equipment transmitting time, and use the quick physical channel (FPACH) that inserts to send to described subscriber equipment, control described subscriber equipment the transmitting time of uplink synchronous physical channel is adjusted; After described Node B had sent Physical Random Access Channel (PRACH), the uplink synchronisation between described subscriber equipment and described Node B was set up at described subscriber equipment.

After uplink synchronisation between described subscriber equipment and described Node B is set up, described Node B is by up closed loop Synchronization Control process, the described subscriber equipment of periodic control is adjusted the transmitting time of its upward signal, to keep the uplink synchronisation between described subscriber equipment and described Node B: for example, between described Node B and described subscriber equipment, set up up and during downward special physical channel (Dedicated Physical Channel), described subscriber equipment, is periodically controlled by described Node B through up closed loop Synchronization Control process the transmitting time of uplink special physical channel; In each up closed loop Synchronization Control cycle, described Node B is after receiving the wireless signal of uplink special physical channel, utilize the instruction row sequence part (Midamble part) in the described uplink special physical channel, channel impulse response (ChannelImpulse Response) to the current wireless channel detects, and the peak-peak position of channel impulse response and the target location (Targetposition) of its setting compared, when described peak-peak position during early than the target location set, described Node B generates adjusts (Synchronization Shift) order " reducing " synchronously, control the transmitting time lead (Timing Advance) that described subscriber equipment reduces uplink special physical channel, when described peak-peak position is later than the target location of setting, described Node B generates synchronization adjustment command " increase ", control the transmitting time lead that described subscriber equipment increases uplink special physical channel, when target location that described peak-peak position equals to set, described Node B generates synchronization adjustment command " constant ", control described subscriber equipment the transmitting time lead of uplink special physical channel is remained unchanged, described synchronization adjustment command sends by downward special physical channel; In each up closed loop Synchronization Control cycle, the synchronous adjustment step-length of described transmitting time lead can be

Or 1 chip (Chip).(see also TD-SCDMA 3-G (Generation Three mobile communication system) standard document 3GPP TS25.221,25.224 and 25.225, the download of document be provided among the www.3gpp.org of 3GPP website).

In wireless communication system, because hypsography, building and other barriers in the wireless transmission environment be to the covering of radio wave, wireless signal can take place to decline at a slow speed when transmitting in wireless channel, is called shadow fading (Shading fading); In addition, again because multipath transmisstion (Multi-path transmission) and Doppler frequency shift (Doppler shift) effect of wireless signal in the wireless channel transmission, wireless signal also can the time of origin territory after wireless channel transmission and frequency domain in quick decline (Fast fading), be referred to as time selective fading (Time selective fading) and frequency selective fading (Frequency selective fading) respectively; The decline at a slow speed and the quick fading characteristic of above-mentioned wireless channel make the impulse response of wireless channel change in time, the transmission characteristic that becomes when having.

In the up closed loop Synchronization Control process of above-mentioned TD-SCDMA 3-G (Generation Three mobile communication system), the frequency of up closed loop Synchronization Control be every 1,2,3 ..., or 8 subframes 1 time, promptly variable between 25～200 times/second, the short period of uplink closed loop is 5ms; When the transmission characteristic of wireless channel changes when very fast, the wireless signal that transmits in the wireless channel can experience described quick decline, at this moment, even described Node B is with the shortest up closed loop Synchronization Control cycle, controlling described subscriber equipment adjusts the transmitting time of uplink special physical channel, may still can't adapt to the variation of wireless channel transmission characteristic, cause of the adjustment of described subscriber equipment to the uplink special physical channel transmitting time, lag behind the variation of wireless channel transmission characteristic, not only cause the decreased performance of up closed loop Synchronization Control process, and the synchronization adjustment command that sends of described Node B even may run counter in the variation of wireless channel transmission characteristic, cause described subscriber equipment that the transmitting time of uplink special physical channel is carried out wrong adjustment, make up closed loop Synchronization Control process lose its due function, cause system performance degradation.

When the transmission characteristic of wireless channel changes when very fast, in the up closed loop Synchronization Control process for above-mentioned TD-SCDMA 3-G (Generation Three mobile communication system), described subscriber equipment lags behind the problem that the wireless channel transmission characteristic changes to the adjustment of uplink special physical channel transmitting time, a kind of solution is: in each up closed loop Synchronization Control cycle, with described closed loop synchronisation control means based on current wireless channel impulse response peak-peak position, change closed loop synchronisation control means into based on the average peak-peak of wireless channel impulse response position, promptly in each up closed loop Synchronization Control cycle, described Node B is after receiving the signal of uplink special physical channel, detect the position of the average peak-peak of wireless channel impulse response in current up closed loop Synchronization Control cycle and several up closed loop Synchronization Control cycles before, for example, peak-peak position to wireless channel impulse response in 15 continuous up closed loop Synchronization Control cycles is detected, when the up closed loop Synchronization Control cycle is 5ms, promptly be to detect the peak-peak position of uplink special physical channel wireless channel impulse response in continuous 15 subframes (for the definition of subframe structure, see also TD-SCDMA 3-G (Generation Three mobile communication system) standard document 3GPP TS 25.221, provide the download of document among the www.3gpp.org of 3GPP website), then described testing result is carried out moving average, the position of the average peak-peak of wireless channel impulse response and the target location of setting are compared, generate synchronization adjustment command.

When adopting the shortest up closed loop Synchronization Control cycle, when described subscriber equipment still lags behind the variation of wireless channel transmission characteristic to the adjustment of uplink special physical channel transmitting time, by above-mentioned closed loop synchronisation control means based on the average peak-peak of wireless channel impulse response position, make up closed loop Synchronization Control process be adapted to the fading characteristic at a slow speed of wireless channel, but not the quick fading characteristic of wireless channel, can reduce the probability that described subscriber equipment is adjusted uplink special physical channel transmitting time mistake, than described closed loop synchronisation control means, can make up closed loop Synchronization Control process obtain preferable performance based on current wireless channel impulse response peak-peak position.

Yet, when the transmission characteristic of wireless channel changes slowly, promptly adopt the described up closed loop Synchronization Control cycle, described subscriber equipment can be adapted to the variation of wireless channel transmission characteristic to the adjustment of uplink special physical channel transmitting time, if still use closed loop synchronisation control means based on the average peak-peak of wireless channel impulse response position, than described closed loop synchronisation control means, can reduce the performance of up closed loop Synchronization Control process again based on current wireless channel impulse response peak-peak position.

Summary of the invention

The object of the present invention is to provide the up closed loop synchronisation control means in the time-division-synchronous CDMA access system, can be according to the variation of wireless channel transmission characteristic, the method of adaptive adjustment closed loop Synchronization Control, thus the performance of up closed loop Synchronization Control process under the different radio channel transfer characteristic improved.

Above-mentioned goal of the invention is realized by following method of the present invention: the up closed loop synchronisation control means in the time-division-synchronous CDMA access system, it is characterized in that in up closed loop Synchronization Control process, after Node B receives the upward signal of subscriber equipment, at first detect or be calculated as follows value:

A. the coefficient correlation ρ of wireless channel transmission characteristic in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle, $\mathrm{\ρ}=\frac{E\{h_t\left(n\right)-E[h_t\left(n\right)\left]\right\}\{h_t(n-1)-E[h_t(n-1)\left]\right\}}{\sqrt{D\left[h_t\left(n\right)\right]}\·\sqrt{D\left[h_t(n-1)\right]}};$ Wherein $h_t\left(n\right)=\frac{h_p\left(n\right)+x_{\mathrm{TA}}\left(n\right)-T_{\mathrm{pos}}}{2};$ h _p(n) and h _p(n-1) represent the peak-peak position of wireless channel impulse response in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle respectively, x _TA(n) and x _TA(n-1) represent the transmission lead of upward signal in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle respectively, T _PosThe target location that the expression Node B is set, n represents the sequence number in current up closed loop Synchronization Control cycle, the mathematic expectaion of E () expression stochastic variable, D () represents variance of a random variable;

The average peak-peak position of b. described wireless channel impulse response

Then, calculate monitoring position

$\widehat{h_p}\left(n\right)=[h_p\left(n\right)-{\stackrel{\‾}{H}}_p]\mathrm{\ρ}+\stackrel{\‾}{H_p};$ The monitoring position of gained and the target location of setting are compared, generate synchronization adjustment command.

According to an aspect of the present invention, when calculating described coefficient correlation ρ, described mathematic expectaion and variance replace with the time average of stochastic variable, described time average is the moving average of stochastic variable in continuous 15 up closed loop Synchronization Control cycles, and described 15 up closed loop Synchronization Control cycles comprise current up closed loop Synchronization Control cycle and 14 up closed loop Synchronization Control cycles before.

According to another aspect of the present invention, described wireless channel impulse response utilizes the instruction row sequence in the described uplink special physical channel partly to detect by described Node B.

According to another aspect of the present invention, the average peak-peak position of described wireless channel impulse response is the moving average of wireless channel impulse response peak-peak position described in continuous 15 up closed loop Synchronization Control cycles, and described 15 up closed loop Synchronization Control cycles comprise current up closed loop Synchronization Control cycle and 14 up closed loop Synchronization Control cycles before.

According to a further aspect of the invention, described target location is set by the physical layer of described Node B.

According to a further aspect of the invention, the transmission lead of described upward signal is periodically sent to by described subscriber equipment in the measurement report of described Node B and obtains.

Specific embodiment

Method of the present invention is applied in the up closed loop Synchronization Control process of TD-SCDMA 3-G (Generation Three mobile communication system).

In a sub-district of TD-SCDMA 3-G (Generation Three mobile communication system), set up up and downward special physical channel between the subscriber equipment in Node B and sub-district, described subscriber equipment is controlled by Node B through up closed loop Synchronization Control process the transmitting time of uplink special physical channel, wherein, the method according to this invention, after described Node B receives the uplink special physical channel signal of described subscriber equipment, at first detect or be calculated as follows value, following n represents the sequence number in current up closed loop Synchronization Control cycle:

A. the coefficient correlation ρ of wireless channel transmission characteristic in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle;

The average peak-peak position of b. described wireless channel impulse response

Calculating described coefficient correlation $\mathrm{\ρ}=\frac{E\{h_t\left(n\right)-E[h_t\left(n\right)\left]\right\}\{h_t(n-1)-E[h_t(n-1)\left]\right\}}{\sqrt{D\left[h_t\left(n\right)\right]}\·\sqrt{D\left[h_t(n-1)\right]}}$ The time, the time average of the mathematic expectaion of stochastic variable and variance available random variable is approximate, for example, stochastic variable in continuous 15 up closed loop Synchronization Control cycles is carried out moving average, and described 15 up closed loop Synchronization Control cycles comprise current up closed loop Synchronization Control cycle and 14 up closed loop Synchronization Control cycles before; $h_t\left(n\right)=\frac{h_p\left(n\right)+x_{\mathrm{TA}}\left(n\right)-T_{\mathrm{pos}}}{2},$ $h_t(n-1)=\frac{h_p(n-1)+x_{\mathrm{TA}}(n-1)-T_{\mathrm{pos}}}{2},$ h _p(n) and h _p(n-1) represent the peak-peak position of wireless channel impulse response in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle respectively, x _TA(n) and X _TA(n-1) represent the transmission lead of upward signal in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle respectively, T _PosThe target location that the expression Node B is set; The average peak-peak position of described wireless channel impulse response

Average for the sliding time of wireless channel impulse response peak-peak position described in continuous 15 up closed loop Synchronization Control cycles, described 15 up closed loop Synchronization Control cycles comprise current up closed loop Synchronization Control cycle and 14 up closed loop Synchronization Control cycles before; The impulse response of described wireless channel utilizes the instruction row sequence in the described uplink physical channel partly to detect; The length of above-mentioned moving average window can be carried out constantly adjustment according to the priori of channel transfer characteristic or prediction.

Then, described Node B utilizes above-mentioned result to calculate monitoring position

$\widehat{h_p}\left(n\right)=[h_p\left(n\right)-\stackrel{\‾}{H_p}]\mathrm{\ρ}+\stackrel{\‾}{H_p};$ The monitoring position of gained and the target location of setting are compared, generate synchronization adjustment command: when described monitoring position during early than the target location set, described Node B generates synchronization adjustment command and " reduces ", control the transmitting time lead that described subscriber equipment reduces uplink special physical channel, when described monitoring position is later than the target location of setting, described Node B generates synchronization adjustment command " increase ", control the transmitting time lead that described subscriber equipment increases uplink special physical channel, when target location that described monitoring position equals to set, described Node B generates synchronization adjustment command " constant ", control described subscriber equipment the transmitting time lead of uplink special physical channel is remained unchanged, described synchronization adjustment command sends by downward special physical channel; In each up closed loop Synchronization Control cycle, the synchronous adjustment step-length of described transmitting time lead can be

Or 1 chip.

In order to obtain the transmission lead x of upward signal in the current up closed loop Synchronization Control cycle _TA(n), described Node B can periodically send from described subscriber equipment the measurement report of (Periodic measurement reporting) and obtains.

By above-mentioned adaptive up closed ring synchronisation control means, as can be seen: when the transmission characteristic of wireless channel changes when very fast, in two adjacent up closed loop Synchronization Control cycles, the correlation of wireless channel transmission characteristic is less, described coefficient correlation ρ will inevitably be less, at described monitoring position

In, the average peak-peak position of described wireless channel impulse response Weights greater than the peak-peak position h of described current wireless channel impulse response _p(n), under limiting case, when the transmission characteristic of wireless channel changes when very fast, the transmission characteristic of wireless channel is separate in adjacent two up closed loop Synchronization Control cycles, and promptly correlation is 0, this moment described monitoring position

Promptly equal the average peak-peak position of described wireless channel impulse response

And when the transmission characteristic of wireless channel changed slowly, in two adjacent up closed loop Synchronization Control cycles, the correlation of wireless channel transmission characteristic was bigger, and described coefficient correlation ρ will inevitably be bigger, at described monitoring position In, the peak-peak position h of described current wireless channel impulse response _p(n) weights are greater than the average peak-peak position of described wireless channel impulse response

Under limiting case, when the transmission characteristic variation of wireless channel was very slow, the transmission characteristic of wireless channel was identical in adjacent two up closed loop Synchronization Control cycles, and promptly correlation is 1, at this moment described monitoring position

Promptly equal the peak-peak position h of described current wireless channel impulse response _p(n).

Therefore, by introducing described coefficient correlation ρ, described Node B can be according to the variation of wireless channel transmission characteristic, adaptive adjustment monitoring position, change when very fast in the transmission characteristic of wireless channel, more average peak-peak position based on described wireless channel impulse response, generate synchronization adjustment command, and when the transmission characteristic of wireless channel changes slowly, more peak-peak position based on described current wireless channel impulse response, generate synchronization adjustment command, thereby method that can adaptive adjustment closed loop Synchronization Control is improved the performance of up closed loop Synchronization Control process under the different radio channel transfer characteristic.

Claims (7)

1. the up closed loop synchronisation control means in the time-division-synchronous CDMA access system is characterized in that after Node B receives the upward signal of subscriber equipment, at first detecting or be calculated as follows value in up closed loop Synchronization Control process:

A. the coefficient correlation ρ of wireless channel transmission characteristic in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle, $\mathrm{\ρ}=\frac{E\{h_t\left(n\right)-E[h_t\left(n\right)\left]\right\}\{h_t(n-1)-E[h_t(n-1)\left]\right\}}{\sqrt{D\left[h_t\left(n\right)\right]}\·\sqrt{D\left[h_t(n-1)\right]}};$ Wherein $h_t\left(n\right)=\frac{h_p\left(n\right)+x_{\mathrm{TA}}\left(n\right)-T_{\mathrm{pos}}}{2};$ h _p(n) and h _p(n-1) represent the peak-peak position of wireless channel impulse response in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle respectively, x _TA(n) and x _TA(n-1) represent the transmission lead of upward signal in current up closed loop Synchronization Control cycle and it previous up closed loop Synchronization Control cycle respectively, T _PosThe target location that the expression Node B is set, n represents the sequence number in current up closed loop Synchronization Control cycle, the mathematic expectaion of E () expression stochastic variable, D () represents variance of a random variable;

The average peak-peak position of b. described wireless channel impulse response

Then, calculate monitoring position

$\widehat{h_p}\left(n\right)=[h_p\left(n\right)-\stackrel{\‾}{H_p}]\mathrm{\ρ}+\stackrel{\‾}{H_p};$ The monitoring position of gained and the target location of setting are compared, generate synchronization adjustment command.

2. the up closed loop synchronisation control means in the time-division-synchronous CDMA access system as claimed in claim 1 is characterized in that described mathematic expectaion and variance replace with the time average of stochastic variable when calculating described coefficient correlation ρ.

3. the up closed loop synchronisation control means in the time-division-synchronous CDMA access system as claimed in claim 2, it is characterized in that described time average is the moving average of stochastic variable in continuous 15 up closed loop Synchronization Control cycles, described 15 up closed loop Synchronization Control cycles comprise current up closed loop Synchronization Control cycle and 14 up closed loop Synchronization Control cycles before.

4. the up closed loop synchronisation control means in the time-division-synchronous CDMA access system as claimed in claim 1 is characterized in that described wireless channel impulse response utilizes the instruction row sequence in the described uplink special physical channel partly to detect by described Node B.

5. the up closed loop synchronisation control means in the time-division-synchronous CDMA access system as claimed in claim 1, the average peak-peak position that it is characterized in that described wireless channel impulse response is the moving average of wireless channel impulse response peak-peak position described in continuous 15 up closed loop Synchronization Control cycles, and described 15 up closed loop Synchronization Control cycles comprise current up closed loop Synchronization Control cycle and 14 up closed loop Synchronization Control cycles before.

6. the up closed loop synchronisation control means in the time-division-synchronous CDMA access system as claimed in claim 1 is characterized in that described target location set by the physical layer of described Node B.

7. the up closed loop synchronisation control means in the time-division-synchronous CDMA access system as claimed in claim 1, the transmission lead that it is characterized in that described upward signal are periodically sent to by described subscriber equipment in the measurement report of described Node B and obtain.