CN101112114A - Method and apparatus for using varying length training sequences in wireless communications - Google Patents

Abstract

The invention discloses a communication method for a wireless communication system, wherein, a received signal from a mobile terminal is detected to obtain a detection result of an uplink channel corresponding to the received signal; determining the length criterion of the training sequence in the corresponding uplink burst according to the detection result of the uplink channel; allocating a predetermined uplink time slot to the mobile terminal according to the length criterion of the training sequence in the uplink burst; and notifying the length criterion of the training sequence in the uplink burst and the uplink time slot to the mobile terminal.

Description

Method and apparatus for using variable length training sequences in wireless communication

technical field

The present invention relates to a wireless communication system, in particular to a communication method and device for adjusting a training sequence in a communication burst and a corresponding resource allocation scheme.

Background technique

In the TDD CDMA system, Midamble (i.e. training sequence code) is a key part of the burst pulse (or other meaning) of the TDD CDMA system, which is used for channel estimation. In conventional systems, Midambles are sent in every data burst. If under low rate of change channel conditions, frequent channel estimation may not be required. In this case, since Midambles are sent frequently (once for each data burst), more business data cannot be accommodated. In the FDD (Frequency Division Duplex, frequency division duplex) mode (for example, in WCDMA, the channel estimation of the dedicated channel is carried by the "pilot" part of each service TS (Time Slot, time slot)), each The "pilot" part of the service TS has the same function as Midamble in TDD (Time Division Duplex, Time Division Duplex) mode. So the CDMA system in FDD mode faces the same problem.

US6724815 discloses a method and apparatus for increasing data rate by reducing training data. EP0615352 discloses a wireless communication system using variable length midamble codes. US5606580 discloses a method for adjusting the length of a data block in a time division multiple access communication system. WO9716046 discloses a variable length burst transmission on the physical layer of a multilayer transmission format.

Variations in the length of the training sequence can introduce interference problems. In the CDMA system, different users use the same time slot through different channel codes. When the training sequences in the communication bursts of different users use different lengths, the training sequences and data between multiple users will interfere. Now There is no such problem solved in the technology.

Therefore, new methods and devices are needed to improve the above-mentioned problems faced by the prior art.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned problems in the prior art, provide a new wireless communication method to increase the capacity of service data, and better solve related problems at the same time.

The present invention provides a communication method for a wireless communication system, comprising the steps of: detecting a received signal from a mobile terminal to obtain a detection result of an uplink channel corresponding to the received signal; As a result of the detection, determine the length criterion of the training sequence in the corresponding uplink burst; allocate a predetermined uplink time slot for the mobile terminal according to the length criterion of the training sequence in the uplink burst; Notifying the mobile terminal of the length criterion of the training sequence in the uplink burst and the uplink time slot.

The present invention provides a network end device for a wireless communication system, wherein the network end includes a network end measurement device, a network end determination device, and a sending device,

The network-side measurement device detects the received signal from the mobile terminal to obtain the detection result of the uplink channel corresponding to the received signal; the network-side determination device determines the corresponding uplink burst according to the detection result of the uplink channel The length criterion of the training sequence in the above; the network side determining means allocates a predetermined uplink time slot for the mobile terminal according to the length criterion of the training sequence in the uplink burst; and the sending means sends the described Notifying the mobile terminal of the length criterion of the training sequence in the uplink burst and the uplink time slot.

The present invention provides a communication method for a wireless communication system, comprising the steps of: determining a length criterion of a training sequence in a corresponding downlink burst according to a downlink channel detection report from a mobile terminal; according to the downlink burst assigning a predetermined downlink time slot to the mobile terminal according to the length criterion of the training sequence; and notifying the mobile terminal of the length criterion of the training sequence in the downlink burst and the downlink time slot.

The present invention provides a network terminal device for a wireless communication system, wherein the network terminal includes a network terminal determining device and a sending device,

The network-side determination device determines the length criterion of the training sequence in the corresponding downlink burst according to the downlink channel detection report from a mobile terminal; the network-side determination device determines the length criterion of the training sequence in the downlink burst according to the described downlink burst, Allocating a predetermined downlink time slot to the mobile terminal; and the sending device notifies the mobile terminal of the length criterion of the training sequence in the downlink burst and the downlink time slot.

The present invention provides a mobile terminal used in a wireless communication system, wherein the mobile terminal includes a receiving device and an adjusting device,

The receiving device receives a notification from the network end equipment, the notification includes the length criterion of the training sequence in the burst and the allocation of time slots,

The adjusting means sets the training sequence according to the length criterion of the training sequence in the burst and the allocation of time slots.

By using the present invention, the length criterion of the training sequence code in the data burst is changed according to the change of the channel quality, and the saved wireless resources can be used to carry more business data to increase the capacity of the business data. Using the present invention, the time slot allocation strategy can also be adjusted according to the length of the training sequence in the burst, and the interference problem caused by the change of the length criterion of the training sequence code in the data burst is solved.

Other objectives and effects of the present invention will become clearer and easier to understand through the following description combined with the accompanying drawings and the contents of the claims, and with a more comprehensive understanding of the present invention.

Description of drawings

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

Fig. 1 shows the subframe structure of TD-SCDMA (Time Division-Synchronous Code Division Multiple Access, Time Division-Synchronous Code Division Multiple Access);

Fig. 2 shows the time slot structure of TD-SCDMA;

Fig. 3 shows the interference between Midamble and service data when multiple user equipments use different Midamble lengths;

FIG. 4 shows specific time slots assigned to user equipments whose Midamble length is 0 (no Midamble) in a data burst according to one embodiment of the present invention;

FIG. 5A is a flowchart of a training sequence scheme in a burst of an uplink time slot according to an embodiment of the present invention;

FIG. 5B is a flowchart of a training sequence scheme in a burst of a downlink time slot according to an embodiment of the present invention;

Fig. 6 is a schematic diagram of functional device configurations of a UE and a network according to an embodiment of the present invention.

The same reference numerals represent the same or corresponding features or functions throughout the drawings.

Detailed ways

In the following embodiments, the present invention is exemplarily described with reference to the accompanying drawings.

The principle of the present invention is described below.

For the uplink burst, according to one of the communication methods of the present invention, the received signal from a mobile terminal is first detected to obtain the detection result of the corresponding uplink channel of the received signal. Then, according to the detection result of the uplink channel, the length criterion of the training sequence in the corresponding uplink burst is determined. Then according to the length criterion of the training sequence in the uplink burst, allocate a predetermined uplink time slot to the mobile terminal. Finally, the mobile terminal is notified of the length criterion of the training sequence in the uplink burst and the uplink time slot.

For the downlink burst, according to one of the communication methods of the present invention, firstly, according to the downlink channel detection report from a mobile terminal, the length criterion of the training sequence in the corresponding downlink burst is determined. Then, according to the length criterion of the training sequence in the downlink burst, a predetermined downlink time slot is allocated to the mobile terminal. Finally, the mobile terminal is notified of the length criterion of the training sequence in the downlink burst and the downlink time slot.

In the communication method of the present invention, the length criterion includes the length of the training sequence, and may also include a period of continuous use of the length of the training sequence. The lengths of the training sequences in the same length criterion are the same or similar. During the communication process, the length of the training sequence can be changed according to the detection result of the channel quality, so as to obtain different length criteria of the training sequence used in the communication burst sent or received by the user equipment. For the case where the length of the training sequence is zero, the number of mobile terminals whose length of the training sequence is zero in the same time slot can also be changed according to the detection result of the channel quality. Channel detection can include SIR, SNR, or SNIR.

The wireless communication system of the present invention is implemented by taking the CDMA mobile communication system as an example.

In the following description, the method of the present invention is described by taking the Midamble (that is, the training sequence) in the burst as an example.

Midamble is a key part of the burst structure in TDD CDMA system and is used for channel estimation. In traditional systems, Midambles are sent once per data burst. The method provided by the invention is to adjust the length criterion of Midamble according to the channel quality. For example, adjust the length of Midamble, the length can be L, 0, or 1/2L. The concept of the length criterion may also include a period of continuous use of a training sequence (Midamble) of a certain length, for example, a training sequence of length L, 0, or 1/2L is used for several consecutive subframes. In the following, the case where the alternate sending length is L and 0 is taken as an example for description. For example, when the channel quality is stable, for bursts in multiple consecutive subframes, bursts in subsequent subframes may use channel estimates obtained based on previous bursts. Therefore, in a burst of multiple subframes, the user can intermittently send Midamble, that is, the length L of the training sequence of a burst in a period (the length is not zero), while the length of the training sequence in the burst of other subframes to zero. In the solution provided by the present invention, the length of the training sequence or the period in the above example is determined by the network according to the detection result. The present invention also provides signaling procedures associated with the related scheme. In addition, when more than one UE adopts different Midmble length criteria, according to the solution provided by the present invention, it is also possible to avoid interference between Midamble and other user data by allocating different time slots to user equipment with the same Midmble length criteria.

In the following part of this application, TD-SCDMA is taken as an example to provide necessary information about the TDD system and describe the idea of the present invention. In fact, what is described here can be extended to high chip rate 7.68 Mchip/s and other TDD CDMA systems with some necessary modifications. Furthermore, with some necessary modifications, the same idea can be extended to FDD mode.

In a TDD CDMA mobile cellular system, signal transmission is carried out by "radio frames". The radio frame is further divided into time slots (TS) to carry information. In the TD-SCDMA system, the length of a radio frame is 10ms and is divided into two identical 5ms subframes. In each subframe, there are 7 normal time slots and 3 special time slots. Figure 1 shows the subframe structure of TD-SCDMA, where TS0 and TS1 are always designated as downlink and uplink time slots, respectively, for uplink and downlink bursts, respectively. DwPTS (Downlink Pilot Time Slot, downlink pilot time slot) and UpPTS (UplinkPilot Time Slot, uplink pilot time slot) are dedicated downlink and uplink pilot time slots, respectively used for downlink The road and uplink are synchronized, and GP (Guard Period) is the guard interval.

In each time slot shown in Figure 2, there are three fields, data part, Midamble, and GP to distinguish different TSs. Midamble (m ₁ , m ₂ , m ₃ , . . . , m _n , n is the Midamble length in chips) is used to estimate the channel state.

The following description utilizes the idea of the present invention to change the sending frequency of Midamble by using the length of the training sequence in the length criterion to be L or zero so as to adapt to the channel state. When it is detected that the UE or BS (Base Station, base station) has better channel quality (for example, the channel changes slowly), there is no need to send Midamble in each data burst, and the previous channel estimation can be used for those Data burst without Midamble (Midamble length is zero). However, this change should be combined with a series of signaling procedures, such as channel state measurement and reporting, parameter change notification, etc. For several UEs in use in one time slot at the same time, in order to eliminate the interference between the local Midamble and other user's data, some schemes are proposed in the present invention. In the following sections, the complete process of the Midamble length criterion of the present invention is described.

The following describes how to use the solution of the present invention to change the Midamble sending frequency.

In the implementation of the present invention, the transmission frequency of Midamble is changed according to the detected wireless link quality. If the detected wireless channel condition is good, or when the channel is almost time-invariant (the channel condition changes very slowly), the Midamble transmission frequency can be reduced, and more business data can be carried using the saved wireless resources. The adjusted Midamble transmission frequency parameters (time slot allocation, etc.) are calculated in the network according to the measurement results, and then send signaling to the UE through the downlink.

The sending frequency of the above Midamble is a specific implementation of the training sequence length criterion. According to the specific implementation described here, the sending frequency of the Midamble is changed, some subframes send the Midamble (the length is L), and some subframes do not send the Midamble (the length is zero). It can also be said that the sending cycle of Midamble has been changed. A period includes subframes with Midamble and subframes without Midamble. In other words, the length of Midamble in some periods in a cycle is not zero, and the length of Midamble in some periods is zero.

Taking the Midamble (training sequence) sending period and the detected wireless link quality as an example, different Midamble sending periods can be set for different signal quality standards, see Table 1.

Table 1 Midamble sending cycle and wireless link status

Wireless link status indicators (can be SIR, SNR, SNIR or other standards, etc., initialized by the network side.) Midamble sending cycle note T ₀ (assumed threshold baseline) Specified sending cycle F: Midamble is sent once during every F data burst. i and j can be determined by the network side. The observation of channel variation (time-varying or time-invariant) is also performed by the network side. In a measurement cycle, the measured radio link state index T is better than T ₀ . Increase the above sending period to F' (for example, F'=F+i, (i=1, 2, 3...)). During a measurement cycle, the measured T is worse than _T0 . Reduce the above sending period to F" (for example, F"=F-j, j=1, 2, 3...). The measured T is very close to T ₀ . Does not change the current Midamble sending frequency.

The following describes a scheme in which multiple UEs occupy one TS at the same time.

The following problems occur when changing Midamble fields.

In fact, in many cases, the mobile terminal will not move very fast and/or the channel condition will not change very frequently, so sending Midamble frequently is unnecessary and wastes radio resources in a sense. In the case that only one UE occupies one time slot, the Midamble principle of the present invention can significantly save radio resources. However, if more than one UE occupies the same time slot and adjusts their Midamble transmission frequency according to the channel quality, two new problems must be solved.

One of the problems is downlink interference with traffic data.

According to the principle of the present invention, the downlink Midamble transmission frequency should be changed according to the transmission environment. However, in a time slot of more than one UE, if Midambles are sent to some UEs but not to others, interference between Midambles and traffic data may occur.

The second problem is uplink interference with business data.

Same as downlink, in slots with more than one UE, if some UEs transmit Midamble and others do not, uplink interference will occur.

Figure 3 shows how interference occurs (both downlink and uplink). It is assumed that UE1 and UE2 do not send Midamble and UE3-UEn send Midamble in the same time slot. It can be seen that the Midamble of UE3-UEn interferes with the corresponding data of UE1 and UE2. The interference may cause the receiver to be unable to demodulate the data of UE1 and UE2, and to correctly estimate the channel parameters of UE1 and UE2.

In order to solve the above problems, some supplementary solutions are proposed for the situation that more than one UE occupies one time slot.

One solution is to allocate special time slots to user equipments with the same or similar Midamble lengths in the burst (for example, the Midamble length is zero).

Firstly, for an uplink burst, a received signal from a UE is detected to obtain a detection result of the corresponding uplink channel of the received signal. Then, according to the detection result of the detected uplink channel, the length criterion of the Midamble in the corresponding uplink burst is determined. Then according to the length criterion of the training sequence in the uplink burst, a predetermined uplink time slot is allocated to the UE. Finally, the UE is notified of the length criterion of the Midamble in the uplink burst and the allocated uplink time slot.

For the downlink burst, firstly, according to the downlink channel detection report from a UE, the length criterion of the Midamble in the corresponding downlink burst is determined. Then, according to the Midamble length criterion in the downlink burst, a predetermined downlink time slot is allocated to the UE. Finally, the UE is notified of the length criterion of the Midamble in the downlink burst and the allocated downlink time slot.

To avoid uplink and downlink interference between Midamble and traffic data from different transmitters, special Midamble-free time slots (downlink and uplink) can be allocated for those data bursts without Midamble pulse. In these special time slots, Midambles are not sent, so there is no interference.

As shown in FIG. 4 , one uplink time slot (such as TS3 ) and one downlink time slot (such as TS6 ) can be assigned as Midamble-free time slots, respectively. For multiple UEs in a good transmission environment, when sending/receiving data containing Midamble, they occupy a normal time slot, and when sending/receiving data without Midamble, they use TS3/TS6.

Note that if more UEs have good channel quality and have lower Midamble transmission frequency, they can be assigned more Many no Midamble slots. As the number of Midamble-free time slots increases, the system capacity will increase.

According to the method provided by the present invention, for the case where only a few UEs share one time slot, the interference can be reduced and the data transmission rate can be increased by adjusting the number of Midambles whose length is 0.

As shown in FIG. 3 , assuming that UE1 and UE2 transmit data in the same time slot while other UEs transmit Midamble, the data of UE1 and UE2 can be regarded as noise for other UEs performing channel estimation. Since the noise is only from two UEs, the noise is tolerable for other UEs that obtain channel characteristics. FIG. 3 takes two UEs adopting the solution of the present invention as an example. The number of UEs using the solution of the present invention can be appropriately increased or decreased according to QoS requirements in practice.

For UE1 and UE2, when detecting their data segments, Midamble of other UEs can also be regarded as noise. Literature M.J.Juntti and B.AaZhang, "Finite Memory-LengthLinear Multiuser Detection for Asynchronous CDMA Communications", IEEE Trans.Commu., Vol.45, no.5, May 1997, pp.611-622 proposed: in more than 6- In the case where 8 symbols are finally sent to ZF-BLE (zero-forced block linear equalizer, zero-forced block linear equalizer), the interfering symbols in the processing window of the multi-user detector (due to multipath and asynchronous generation) Almost no impact on the test results. Therefore, if the midamble-free data burst is properly divided into two groups (each group is more than 8 symbols), the midamble of other UEs can be regarded as multipath interference. By sending the two data groups to ZF-BLE respectively, the interference of Midamble of other UEs on UE1 and UE2 can be ignored.

The scheme of the present invention is generally described below.

Fig. 5A is a flow chart of a midamble scheme in a burst of an uplink time slot according to an embodiment of the present invention. FIG. 5B is a flow chart of a midamble scheme in a burst of a downlink time slot according to an embodiment of the present invention.

Fig. 6 shows the configuration of the processing device of the present invention, wherein the network end equipment 100' for the wireless communication system includes a receiving device 101', a measuring device 102', a determining device 103', and a sending device 104'. The mobile terminal UE100 includes a receiving device 101 , a measuring device 102 , an adjusting device 103 , and a sending device 104 .

The working steps and functional devices of the present invention will be described below in conjunction with FIG. 5A, 5B and FIG. 6 . Since the sending frequency of Midamble changes according to the actual wireless transmission environment, the signaling process associated with the Midamble length criterion scheme is necessary. Compared with the traditional solution, the configuration of the processing device at the UE and the network side should be modified in the new solution.

According to an embodiment of the present invention, the receiving device 101' receives a signal from the UE100 (corresponding to step S0 in FIG. 5A), and the measuring device 102' detects the received signal from the UE100 to obtain the corresponding uplink channel of the received signal. Detection result (complete the function of step S1 in Fig. 5A). The determining means 103' determines the Midamble in the corresponding uplink burst, that is, the length criterion of the training sequence according to the detection result of the uplink channel, and is used to change its transmission length, and optionally, change the period during which it continues to use the length of the training sequence ( Complete the function of step S2 in Fig. 5A). The determining means 103' allocates a predetermined uplink time slot to the UE 100 according to the determined Midamble length criterion in the uplink burst (step S3 in Fig. 5A is completed). The sending device 104' notifies the UE100 of the sending frequency and the uplink time slot of the Midamble in the uplink burst (completes the function of step S4 in FIG. 5A ).

In addition, according to a further implementation of the present invention, in the network end equipment 100' used in the wireless communication system, the receiving means 101' receives the downlink channel detection report from the UE100 (completes the function of step S1A in FIG. 5B ). The determination means 103' determines the Midamble, that is, the length criterion of the training sequence according to the downlink channel detection report, and is used to change the Midamble length criterion in the corresponding downlink burst (complete the function of step S2' in Figure 5B). The determining means 103' allocates a predetermined downlink time slot to the UE100 according to the Midamble length criterion in the downlink burst (completes the function of step S3' in FIG. 5B ). The sending device 104' notifies the UE100 of the Midamble length criterion in the downlink burst and the downlink time slot (completes the function of step S4' in FIG. 5B ).

A mobile terminal UE100 for a wireless communication system includes a receiving device 101, an adjusting device 103, a measuring device 102, and a sending device 104, and the receiving device 101 receives a notification from a network end device (corresponding to FIG. 5A and FIG. The functions of steps S4 and S4' in 5B at the receiving end), the notification includes the aforementioned Midamble length criterion and allocation of time slots. The adjustment means 103 receives or sends bursts according to the Midamble length criterion in the received notification and the allocation of time slots (corresponding to the functions of steps S5 and S5' in Fig. 5A and Fig. 5B ). The measurement device 102 detects the downlink channel to obtain a downlink channel detection report (complete the function of step S1' in FIG. corresponding function).

The length of the training sequence in the burst can be any certain length including 0 and the traditional standard length L. The following only takes the case where the length is 0 and L changes alternately (that is, the sending frequency of Midamble) as an example for illustration.

The setting of the training sequence length criterion changes the sending frequency of Midamble. According to the above specific implementation, the sending frequency of the Midamble is changed, some subframes send the Midamble, and some subframes do not send the Midamble. It can also be said that the sending cycle of Midamble has been changed. A period includes subframes with Midamble and subframes without Midamble.

It can be seen from Figures 5A and 5B that the length criteria of the training sequence in the uplink burst and downlink burst and the corresponding time slot resources are determined by the network according to the channel detection results and sent to the mobile terminal through the downlink. Since the characteristics of the downlink and uplink in the TDD system are basically symmetrical, the measurement results of the uplink are almost consistent with those of the downlink. Therefore, the network end device 100' can determine the uplink Midamble length criterion, so as to determine its transmission frequency accordingly.

The extension of the present invention to FDD is described below.

In the FDD mode (for example, in WCDMA, the channel estimation of the dedicated channel is realized through the "pilot" part of each service time slot), the "pilot" has the same function as the Midamble in the TDD mode. So the idea of the present invention can be applied to FDD mode. Due to the different channel characteristics of the uplink and downlink in FDD, the UE100 determines the Midamble length criterion of the uplink by the adjustment device 103 according to the measurement result of the measurement device 102, and the network end device 100' determines the Midamble length criterion of the uplink according to the measurement result of the measurement device 102' The determining means 103' determines a downlink Midamble length criterion.

Many other changes or modifications can be made without departing from the spirit and scope of the present invention. Those skilled in the art should understand that the present invention is not limited to specific embodiments, and the protection scope of the present invention should be determined by the contents of the appended claims.

Claims (28)

1. A communication method for a wireless communication system, comprising the steps of: (a) Detecting a received signal from a mobile terminal to obtain a detection result of an uplink channel corresponding to the received signal; (b) determining the length criterion of the training sequence in the corresponding uplink burst according to the detection result of the uplink channel; (c) assigning a predetermined uplink time slot to the mobile terminal according to the length criterion of the training sequence in the uplink burst; and (d) Notifying the mobile terminal of the length criterion of the training sequence in the uplink burst and the uplink time slot. 2. The communication method according to claim 1, wherein said length criterion comprises the length of the training sequence. 3. The communication method according to claim 2, wherein said length criterion further comprises a period of continuous use of the length of said training sequence. 4. The communication method according to claim 2, wherein the lengths of the training sequences in the same length criterion are the same. 5. The communication method according to claim 2, wherein the length of the training sequence is zero. 6. The communication method according to claim 5, further comprising changing the number of mobile terminals whose training sequence length is zero in the wireless communication system according to the detection result. 7. The communication method according to claim 2, wherein, in the predetermined uplink time slot, all communication bursts have the same training sequence length criterion. 8. The communication method according to claim 1, wherein the detection of the uplink channel includes SIR, SNR, or SNIR. 9. The communication method according to claim 1, wherein said wireless communication system is a CDMA mobile communication system. 10. A network end device for a wireless communication system, wherein the network end includes a network end measurement device, a network end determination device, and a sending device, and the network end measurement device is used for receiving signals from mobile terminals performing detection to obtain a detection result of the uplink channel corresponding to the received signal; The network-end determination device determines the length criterion of the training sequence in the corresponding uplink burst according to the detection result of the uplink channel; The network-side determining device allocates a predetermined uplink time slot to the mobile terminal according to the length criterion of the training sequence in the uplink burst; and The sending device notifies the mobile terminal of the length criterion of the training sequence in the uplink burst and the uplink time slot. 11. The network end device according to claim 10, wherein said length criterion comprises a length of a training sequence. 12. The network end device according to claim 11, wherein said length criterion further comprises a period of continuous use of the length of said training sequence. 13. The network end device according to claim 11, wherein the training sequences in the same length criterion have the same length. 14. The network side device according to claim 11, wherein the length of the training sequence is zero. 15. The network terminal device according to claim 14, the network terminal determining means also changes the number of mobile terminals whose training sequence length is zero in the wireless communication system according to the detection result. 16. The network terminal device according to claim 11, wherein, in the predetermined uplink time slot, all communication bursts have the same training sequence length criterion. 17. A communication method for a wireless communication system, comprising the steps of: (a) according to the downlink channel detection report from a mobile terminal, determine the length criterion of the training sequence in the corresponding downlink burst; (b) assigning a predetermined downlink time slot to the mobile terminal according to the length criterion of the training sequence in the downlink burst; and (c) Notifying the mobile terminal of the length criterion of the training sequence in the downlink burst and the downlink time slot. 18. The communication method according to claim 17, wherein said length criterion comprises the length of a training sequence. 19. The communication method according to claim 18, wherein said length criterion further comprises continuing to use the length of said training sequence for a period of time. 20. The communication method according to claim 18, wherein the training sequences in the same length criterion have the same length. 21. The communication method according to claim 18, wherein the length of the training sequence is zero. 22. The communication method according to claim 21, further comprising changing the number of mobile terminals whose training sequence length is zero in the wireless communication system according to the detection result. 23. The communication method according to claim 18, wherein, in the predetermined downlink time slot, all communication bursts have the same training sequence length criterion. 24. The communication method according to claim 17, further comprising receiving a downlink channel detection report from a mobile terminal. 25. A network end device for a wireless communication system, wherein the network end includes a network end determining device, and a sending device, The network-side determining device determines a length criterion of a training sequence in a corresponding downlink burst according to a downlink channel detection report from a mobile terminal; The network-side determining device allocates a predetermined downlink time slot to the mobile terminal according to the length criterion of the training sequence in the downlink burst; and The sending device notifies the mobile terminal of the length criterion of the training sequence in the downlink burst and the downlink time slot. 26. The network terminal device according to claim 25, further comprising a receiving means for receiving a downlink channel detection report from a mobile terminal. 27. A mobile terminal for a wireless communication system, wherein said mobile terminal comprises a receiving device, and an adjusting device, The receiving device receives a notification from the network end equipment, the notification includes the length criterion of the training sequence in the burst and the allocation of time slots, The adjustment means receives or sends the burst according to the length criterion of the training sequence in the burst in the received notification and the allocation of time slots. 28. The mobile terminal according to claim 27, wherein the mobile terminal further comprises a detection means, and a sending means, The detection device detects the downlink channel to obtain a downlink channel detection report, and the sending device sends the detection report to the network end equipment.

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