CN101047432A - Method for distributing uplink resource - Google Patents

Abstract

The invention discloses a method for allocating uplink resources: the base station calculates and obtains the collision rate of the current frame of a specific uplink message sent by multiple user equipments, judges whether the collision rate is not within the set threshold range, and if so, adjusts the next The uplink time slot or/and sending back-off window occupied by the frame-specific uplink message, the adjusted uplink time slot occupied by the specific uplink message and the sending back-off window information are sent to the user equipment in the next frame through the downlink message, and the user equipment The specific uplink message is sent in the next frame using the adjusted uplink time slot and a sending opportunity in the sending backoff window. The method enables the base station to dynamically allocate uplink resources for specific uplink messages according to the performance of the current license-free system, and meets the requirement of optimal performance of the license-free system.

Description

A method for allocating uplink resources

technical field

The present invention relates to a method for allocating wireless resources, in particular to a method for allocating uplink resources.

Background technique

Currently there are some license-exempt systems, such as wireless area network (WRAN) systems. Among them, WRAN technology is an emerging network technology that provides high-bandwidth and wide-range coverage for remote areas and low-density population areas. WRAN is a license-free operating network, that is, its operating frequency band does not require authorization. It uses cognitive radio technology to find the current free frequency band occupied by unlicensed users (LU) for communication, such as wireless digital television (DTV) Among the licensed frequency bands, an unoccupied frequency band is searched for as the bearer frequency band of the WRAN.

WRAN uses Orthogonal Frequency Division Multiple Access (OFDMA) technology based on Time Division Duplex (TDD) for communication. The frame structure used by WRAN is as follows: each frame is divided into two subframes, one of which is a downlink subframe. The guard time is followed by an uplink subframe. The downlink subframe includes a preamble, a frame control header (FCH), a DS-MAP message indicating how to allocate downlink wireless resources, a US-MAP message indicating how to allocate uplink wireless resources, a downlink channel description (DCD) message, and an uplink channel Description (UCD) message and downlink PHY protocol data unit (PDU); uplink subframe includes initialization message (Initialization), bandwidth resource request message (BW request), emergency coexistence environment notification message (UCS Notification) and sent by different user equipment Uplink PHY PDU. Among them, the US-MAP message is used to indicate which uplink time slots and how wide the uplink time slots occupied by the Initialization, BWrequest, UCS Notification and uplink PHY PDU in the downlink frame are sent; Initialization is used for initial synchronization between the user equipment and the base station to which it belongs; BWrequest is used for the user equipment to request uplink bandwidth resources from the base station to which it belongs; UCS Notification is used for the user equipment to report to the base station the emergency coexistence with the LU when the LU is detected. In each frame, the guard time inserted between the uplink subframe and the downlink subframe is used to ensure that the base station has enough time to change from sending to receiving. Similarly, there is also a guard time between the uplink subframe of the current frame and the downlink subframe of the next frame, and the guard time is used to ensure that the base station can receive messages sent by all user equipments.

At present, the base station can use the above-mentioned frame structure to construct the message sent to the user equipment, such as sending a US-MAP message, which can respectively carry the frequency band of the uplink time slot occupied by the Initialization, BW request, and UCS Notification that the user equipment can send to the base station and Occupies the width of the uplink time slot. Usually, the base station allocates fixed-width uplink time slots for Initialization, BW request, and UCSNotification and notifies the user equipment through a US-MAP message, and the user equipment determines the uplink time slots occupied by Initialization, BW request, and UCSNotification according to the US-MAP message, These specific uplink messages are sent to the base station through corresponding uplink time slots respectively.

Of course, the above frame structure is not only the frame structure adopted by the WRAN system, but also the frame structure adopted by other license-free systems.

However, there are disadvantages in the base station's method of allocating fixed-width uplink time slots for these uplink messages: first, these specific uplink messages are based on contention, and there will be multiple user equipments in the allocated corresponding uplink time slots to send When the base station sends these specific uplink messages, it is easy to cause conflicts, especially when there are many user equipments residing on a base station, which will make the base station unable to correctly receive the specific uplink messages sent by all user equipments; secondly, when these specific uplink messages When the time slot occupied by the uplink message is affected by multipath and noise, the base station cannot detect when the transmission quality is relatively poor; thirdly, when the time slot occupied by these specific uplink messages is interfered by the LU, the transmission quality is poor, The base station cannot detect and cannot reallocate the corresponding time slot.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method for allocating uplink resources, which can enable the base station to dynamically allocate uplink resources for specific uplink messages according to the performance of the current license-free system, and meet the requirements of optimal performance of the license-free system.

According to above-mentioned purpose, technical scheme of the present invention is achieved like this:

A method for allocating uplink resources, characterized in that the method comprises:

The base station calculates the collision rate of the current frame of the specific uplink message sent by multiple user equipments, judges whether the collision rate is not within the set threshold range, and if so, adjusts the uplink time slot or/or the specific uplink message of the next frame and send back-off window, send the adjusted uplink time slot occupied by the specific uplink message and send back-off window information to the user equipment in the next frame through the downlink message, and the user equipment uses the adjusted uplink time slot and send the back-off window information in the next frame One sender within the backoff window will send a specific upstream message.

The process of calculating the conflict rate of the current frame is:

The base station separately counts the error-received specific uplink message counter and the processing completed specific uplink message counter;

A. The base station processes the specific uplink message received from the user equipment in each sending opportunity of the uplink time slot occupied by the specific uplink message of the current frame. After the processing is completed, the counter of the specific uplink message is incremented by 1. If the analysis is not obtained Correct specific uplink message, go to step B;

B. The base station judges whether the power of the data symbol received at the sending opportunity is greater than the set threshold value, and if so, adds 1 to the wrongly received specific uplink message counter;

C. The base station calculates the specific uplink message collision rate according to the error received specific uplink message counter and the processed specific uplink message counter.

The base station also counts the correctly received specific uplink message counter and the empty received specific uplink message counter, wherein,

In step A, it also includes: if the correct specific uplink message is obtained through parsing, adding 1 to the count of correctly received specific uplink message;

In step B, it also includes, if not, adding 1 to the empty received specific uplink message counter.

The threshold value in step B is set according to the background noise of the license-free system and the receiving sensitivity of the license-free system.

The process of calculating the specific uplink message collision rate described in step C is:

The specific uplink message collision rate is equal to the value obtained by dividing the wrongly received specific uplink message counter by the processed specific uplink message counter.

The base station is also provided with a specific uplink message collision rate calculated in the previous frame, and the process of calculating the specific uplink message collision rate in step C is as follows:

Specific uplink message collision rate = a × fixed value and specific uplink message collision rate calculated in the previous frame + (1-a) × wrongly received specific uplink message counter/processing completed specific uplink message counter, where a is 0 to 1 Between, fixed coefficients determined by the license-exempt system according to the smoothing requirements of the transmitted data.

The threshold range is set according to the load balancing requirement of the license-free system, and is a percentage value.

The process of adjusting the uplink time slot or/and sending backoff window occupied by the specific uplink message of the next frame is:

Judging whether the collision rate is greater than the upper limit of the threshold range, if so, increasing the width of the uplink time slot occupied by the next frame specific uplink message or/and increasing the sending back-off window;

Judging whether the collision rate is less than the lower limit of the threshold range, if so, reducing the width of the uplink time slot occupied by the next frame specific uplink message or/and reducing the sending backoff window;

According to the scheduled quiet time, it is detected whether there is licensed user interference on the frequency band occupied by the uplink time slot occupied by the specific uplink message or the channel interference or fading value of the frequency band is greater than the set value. The occupied uplink time slot is adjusted to the frequency band where the unlicensed user interference or channel interference is not greater than the set value.

The process of adjusting the uplink time slot or/and sending backoff window occupied by the specific uplink message of the next frame is:

C1. Judging whether the conflict rate is greater than the upper limit of the threshold range, if yes, execute step C2;

C2. According to the scheduled quiet time, detect whether there is licensed user interference on the frequency band occupied by the uplink time slot occupied by the specific uplink message, or the channel interference or fading value of the frequency band is greater than the set value, and if so, send the next frame specific uplink The uplink time slot occupied by the message is adjusted to the frequency band where the unlicensed user interference or the channel interference of the frequency band is not greater than the set value; if not, then increase the width of the uplink time slot occupied by the next frame specific uplink message Large or/and the send backoff window is increased.

The specific uplink message is an initialization message Initialization, a bandwidth resource request message BWrequest, or an emergency coexistence environment notification message UCS Notification.

It can be seen from the above scheme that the base station of the present invention calculates the collision rate of a specific uplink message in the current frame, and judges whether the calculated collision rate reaches a preset threshold range, and if so, adjusts the specific uplink message occupied by the next frame. uplink time slot or/and send back-off window. Therefore, the method provided by the present invention enables the base station to dynamically allocate uplink resources for specific uplink messages according to the performance of the current license-free system, so as to meet the requirement of optimal performance of the license-free system.

Description of drawings

Fig. 1 is a flowchart of a method for allocating uplink resources for a specific uplink message in the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail by giving specific embodiments and referring to the accompanying drawings.

In order to enable the base station to dynamically allocate uplink resources for specific uplink messages according to the performance of the current license-free system, the inventive base station calculates the collision rate of specific uplink messages in the current frame, and judges whether the calculated collision rate reaches a preset threshold range, and if so, Then adjust the uplink time slot or/and sending backoff window occupied by the specific uplink message in the next frame.

Specifically, the base station of the present invention detects in the current frame whether the uplink time slots allocated to the user equipment to send these specific uplink messages meet the requirements, that is, the multiple specific uplink messages sent by multiple user equipments through the corresponding uplink time slots will not When a conflict occurs, the base station can correctly analyze and obtain multiple specific uplink messages sent by multiple user equipments on the corresponding uplink time slot. If so, the base station continues to judge whether the corresponding uplink time slot has fully met the needs of sending specific uplink messages. , if yes, adjust the uplink time slots and/or send back-off windows allocated to the user equipment to send these specific uplink messages in the next frame, if not, then do not adjust the uplink time slots allocated to the user equipment to send these specific uplink messages in the next frame The uplink time slot and/or the sending back-off window are adjusted; if not, the base station adjusts the uplink time slot and/or sending back-off window allocated to these specific uplink messages sent by the user equipment in the next frame.

In the present invention, the sending opportunity refers to the number of specific uplink messages that the base station can theoretically receive in the current frame, which increases according to the increase of the uplink time slot width; The information sent indicates how many sending opportunities are allocated to the user equipment. After receiving the sending back-off window, the user equipment randomly selects a sending opportunity to send a specific uplink message. The smaller the sending back-off window set by the base station, the user equipment sends a specific uplink message. The probability of sending an uplink message is also greater.

Fig. 1 is a flow chart of the method for allocating uplink resources for a specific uplink message according to the present invention, and its specific steps are:

Step 100, the base station sends information about the uplink time slot occupied by the specific uplink message of the current frame and the information of the transmission opportunity in the occupied uplink time slot to the user equipment through a downlink message.

In the present invention, the information of the uplink time slot occupied by the specific uplink message of the current frame can be sent through the US-MAP message in the downlink message of the current frame, including the width of the uplink time slot occupied and the location of the uplink time slot occupied. frequency band.

The information of the sending opportunity in the occupied uplink time slot can be sent through the UCD message in the downlink message of the current frame. The information of the sending opportunity is actually controlled by a sending fallback window in the prior art. The fallback window has two parameters, The start parameter of the fallback window and the end parameter of the fallback window can take values from 0 to 15. According to the values of these two parameters, the user equipment can randomly select a sending opportunity from the sending opportunities in the sending fallback window to send a specific uplink information. If the sending backoff window is increased, the sending probability will decrease for the user equipment; if the sending backoff window is decreased, the sending probability will be increased for the user equipment.

Step 101 , the base station counts the counters of the specific uplink message correctly received, the counter of the specific uplink message received incorrectly, the counter of the specific uplink message received empty, and the counter of the specific uplink message processed completely.

Step 102, if the base station analyzes the specific uplink message in the sending opportunity of the uplink time slot occupied by the specific uplink message of the current frame, it will add 1 to the counter of the correctly received specific uplink message and the counter of the specific uplink message that has been processed; If no specific uplink message is found, go to step 103.

Step 103 , the base station judges whether the power of the data symbol received at the sending opportunity is greater than a set threshold value, if yes, execute step 104 ; otherwise, execute step 105 .

Equation (1) to calculate the power of a received data symbol is:

Among them, k represents the subcarrier position of the data symbol in OFDM modulation, and i belongs to the time slot position of the data symbol in OFDM modulation.

The set threshold value is set according to the background noise of the license-free system and the receiving sensitivity of the license-free system.

In step 104, the base station adds 1 to the counter of the specific uplink message received incorrectly and the counter of the specific uplink message processed completely.

Step 105, the base station adds 1 to the counter of the empty received specific uplink message and the counter of the processed specific uplink message respectively.

Step 106: After the base station completes the processing of the received specific uplink message in all the sending opportunities of the uplink time slot occupied by the specific uplink message of the current frame, it is calculated according to the error received specific uplink message counter and the processed specific uplink message counter Determine whether the collision rate of the uplink message is not within the set threshold range, if yes, execute step 107; otherwise, execute step 108.

The formulas for calculating the specific uplink message collision rate are formula (2) and formula (3):

Collision rate (collisionRate) = error receiving specific uplink message counter (ReceiveErrorCount)/processing complete specific uplink message counter (TotalOppCount) (2);

collisionRate=a*(collisionRate of the previous frame)+(1-a)*ReceiveErrorCount/TotalOppCount, (3), where a is a fixed coefficient set by the license-free system, between 0 and 1, and the a is smooth with the data The larger the value of a, the better the smoothing, but the worse the timeliness of the data. Conversely, the smaller the value of a, the worse the smoothing, and the better the timeliness of the data.

If the base station has stored the specific uplink message collision rate of the previous frame, the specific uplink message collision rate of the current frame can be calculated according to formula (3), so that the calculation will be more accurate. If the base station does not store the specific uplink message collision rate of the previous frame rate, the specific uplink message collision rate of the current frame can be calculated according to formula (2).

In the present invention, the specific uplink message collision rate is actually the specific uplink message collision probability.

The present invention sets a threshold range, including the upper limit of the threshold range and the lower limit of the threshold range. The threshold range is determined according to the load balancing requirement of the license-free system and is a percentage value.

Step 107, the base station adjusts the uplink time slot or/and sending back-off window occupied by the specific uplink message in the next frame, and sends the adjusted uplink time slot occupied by the specific uplink message to the user equipment in the next frame through the downlink message and sends back The information of the back-off window, the user equipment uses the adjusted uplink time slot and one sending opportunity in the sending back-off window to send a specific uplink message in the next frame.

Step 108, the base station does not adjust the uplink time slot or/and transmission fallback window occupied by the specific uplink message in the next frame, and sends the unadjusted uplink time slot and transmission window occupied by the specific uplink message to the user equipment in the next frame through the downlink message For the information of the backoff window, the user equipment uses an unadjusted uplink time slot and a sending opportunity in the sending backoff window to send a specific uplink message in the next frame.

When the specific uplink message collision rate of the current frame is greater than the upper limit of the threshold range set by the base station, it may indicate that the width of the uplink time slot allocated to the specific uplink message in the current frame is too narrow or/and the sending backoff window is too small, resulting in a specific The uplink message conflicts, and the solution is: increase the width of the uplink time slot allocated to the specific uplink message in the next frame or/and increase the sending backoff window. The process of increasing the sending back-off window is: resetting the two parameters of the sending back-off window that contains the opportunity to send, that is, setting the value of the start parameter setting of the sending back-off window to be smaller than that set in the current frame and ending the sending back-off window The value of the parameter is set larger than that of the current frame, thereby reducing the sending probability.

When the specific uplink message collision rate of the current frame is greater than the upper limit of the threshold range set by the base station, it may also indicate that the frequency band where the uplink time slot allocated to the specific uplink message in the current frame is located is interfered by LU. In this case, the existing technology needs to be adopted Scheduling Quiet Time (QP) sensing detects whether there is LU interference, and if so, adjusts the frequency band where the uplink time slot allocated to a specific uplink message in the next frame is located so that the frequency band where it is located has no LU interference.

Since the specific uplink message collision rate of the current frame is greater than the upper limit of the threshold range set by the base station, there are two possibilities and two solutions, so the present invention can also first determine Whether there is LU interference in the frequency band where the uplink time slot allocated to a specific uplink message in the current frame is located, if so, adjust the frequency band; otherwise, adjust the width or/and sending opportunity of the uplink time slot allocated to a specific uplink message The way.

When the specific uplink message collision rate of the current frame is greater than the upper limit of the threshold range set by the base station, there is another possibility that the subchannel where the uplink time slot allocated by the specific uplink message of the current frame is located has serious fading. At this time, the base station needs to Perform channel estimation according to the prior art, if it is determined that the set fading value is reached, then adjust the subchannel where the uplink time slot assigned by the specific uplink message of the current frame is located, and adjust to a subchannel with less severe fading.

When the specific uplink message collision rate of the current frame is less than the lower limit of the threshold range set by the base station, it may indicate that the width of the uplink time slot allocated to the specific uplink message in the current frame is too large or/and the sending backoff window is too small, resulting in The waste of resources can be solved by narrowing the width of the uplink time slot allocated to the specific uplink message in the next frame or/and reducing the sending backoff window. The process of increasing the sending back-off window is: re-setting the two parameters of the back-off window containing the opportunity to send, that is, setting the value of the start parameter of the send back-off window to be larger than the current frame setting and the end parameter of the send back-off window The value set is smaller than the current frame setting, thereby increasing the sending probability. Narrowing the width of the uplink time slot allocated to the specific uplink message in the next frame can save uplink resources, and increasing the sending probability can make the user equipment speed up the speed of sending the specific uplink message.

In the present invention, the specific uplink message is Initialization, BW request or UCSNotification, and these messages are used as examples below to describe the methods provided by the present invention in WRAN in detail.

Allocation of UCS uplink time slots occupied by UCS Notification

When the user equipment detects that there is an LU, if the uplink channel has been allocated, the UCS Notification is sent to the base station in the allocated uplink channel; if the uplink channel is not allocated, the UCS Notification is sent on the allocated UCS uplink time slot to the base station.

When the UCS Notification is sent on the allocated UCS uplink time slot, it only carries a common medium access control (MAC) header, which is used to identify the message that the frequency band occupied by the LU is detected. The message can be encrypted and set in the common In the MAC header, the PDU including the LU interference report is not carried.

The base station detects the UCSNotification that may be sent by the user equipment at each sending opportunity of the UCS uplink time slot. On each sending opportunity of the UCS uplink time slot, there may be a UCSNotification, or there may be no UCS Notification, and there may be multiple UCSNotifications occurring. conflict situation. Therefore, for each sending opportunity in the UCS uplink time slot, the processing process of the base station is:

Parse the UCS Notification on each sending opportunity of the UCS uplink time slot.

When the UCS Notification can be parsed, add 1 to the set counter (ReceiveValidUSCCount) that correctly receives the UCSNotification, and add 1 to the set counter (TotalUSCOppCount) that completes a UCS Notification.

When a UCS Notification cannot be resolved, then calculate the power of data symbols on that transmit opportunity, which are modulated into the frequency domain of Orthogonal Frequency Division Multiplexing (OFDM), and may span the assigned USC The data symbol of the uplink time slot, specifically:

Among them, k represents the subcarrier position of the data symbol in OFDM modulation, and i belongs to the time slot position of the data symbol in OFDM modulation.

The base station compares the calculated Power with the threshold P1, where the threshold P1 is determined according to the background noise of the WRAN system and the receiving sensitivity of the WRAN system.

If the Power is greater than P1, the possible reason is that multiple UCS Notifications sent by different user equipments collide, but it may also be that LU interference has occurred on the frequency band where the UCS uplink time slot is located, or on this sending opportunity. deep fading. Regardless of the reason, handle this situation according to the conflict, that is, add 1 to the counter (ReceiveErrorUSCCount) of the set error receiving UCS Notification, and add 1 to TotalUSCOppCount;

If Power is not greater than P1, then the reason is that no user equipment sends UCS Notification on this sending opportunity, add 1 to the set counter (ReceiveNullUSCCount) that has not received UCS Notification, and add 1 to TotalUSCOppCount.

In this way, the base station can calculate the receiving performance of the current frame for receiving the UCSNotification on the UCS uplink time slot, and this process will be described in detail below.

Use the following formula to calculate the UCS Notification collision rate (USCcollisionRate) of the current frame on the UCS uplink time slot:

USCcollisionRate=ReceiveErrorUSCCount/TotalUSCOppCount

In addition, to make the calculated USCcollisionRate more accurate, the USCcollisionRate of the current frame can be correlated with the USCcollisionRate of the previous frame. If the base station did not adjust the width of the UCS uplink time slot and the size of the UCS fallback window in the previous frame, the USCcollisionRate of the current frame is calculated as follows:

USCcollisionRate=a*(USCcollisionRate of the previous frame)+(1-a)*ReceiveErrorUSCCount/TotalUSCOppCount, where a is a fixed coefficient set by the WRAN system, which is between 0 and 1. This a is related to the data smoothing requirement, a The larger the value, the better the smoothing, but the worse the timeliness of data. Conversely, the smaller the value of a, the worse the smoothing, and the better the timeliness of data.

If the calculated USCcollisionRate is greater than the upper limit R1 of the set threshold range, such as 85%, and the R1 is set according to the load balancing capability of the WRAN system, then the possible reason is that the UCS Notification is allocated in the UCS uplink time slot of the current frame There are too few sending opportunities, causing collisions between UCS Notifications sent by multiple user equipments in the UCS uplink time slot of the current frame. At this time, the base station can adjust the UCS uplink time slot of the next frame, and the adjustment process is as follows:

The base station increases the width of the UCS uplink time slot in the next frame, so that more different user equipments can send more UCS Notifications respectively, such as doubling the width of the UCS uplink time slot in the next frame. Since UCS Notification is an emergency notification and does not require a response from the base station, the width of the UCS uplink time slot cannot be adjusted too large by the base station. Therefore, the base station increases the width of the UCS uplink time slot or does not increase the width of the UCS uplink time slot. , you can also increase the UCS sending backoff window for receiving UCD Notification, that is, set the UCS Notification Backoff Start (UCS Notification Backoff Start) and UCS Notification Backoff End (UCS Notification Backoff End) of the sending backoff window for receiving UCD Notification respectively. Two parameters, the change of these two parameters also means that the probability of each user equipment in the current frame UCS transmission opportunity is reduced, that is, a wider range of transmission opportunities is selected for UCS Notification transmission. Therefore, the present invention alleviates the situation that the UCS uplink time slot in the next frame is not enough for multiple user equipments by enlarging the width of the UCS uplink time slot and the size of the UCS sending fallback window.

If the calculated USCcollisionRate is less than the lower limit R2 of the threshold range, such as 30%, the WRAN system has already met the current UCS Notification sending needs, and at this time, it can be considered to reduce the occupation of UCS uplink time slots for the entire WRAN system resources. In addition, consideration should also be given to It is necessary to send UCSNotification to the base station as soon as possible, so consider reducing the width of the UCS uplink time slot at this time, or/and speed up the speed of user equipment reporting UCSNotification by adjusting the size of the UCS sending back-off window.

After the width of the UCS uplink time slot of the previous frame or several frames is increased and the sending back-off window is increased, the USCcollisionRate of the UCS uplink time slot of the current frame is still greater than the set R1, so the possible reason is that the UCS of the current frame The channel status of the uplink time slot is relatively poor, and the interference of the LU to the current WRAN system may also occur. Therefore, the present invention needs a solution, and the solution is as follows.

Schedule QP according to the normal process to detect whether there is LU interference on the current communication frequency band, and if so, adjust the frequency band where the UCS uplink time slot is located. For example, if the frequency band interfered by the LU is 1 MHz, and the UCS uplink time slot of the current frame is located in the first 1 MHz frequency band, then the UCS uplink time slot is adjusted to be within the third 1 MHz partial bandwidth.

During the above adjustment, it may be considered to change the frequency bands of the three uplink time slots for sending Initialization, UCS Notification and BWRequest together, or separately change the frequency band for the uplink time slots for sending UCSNotification.

Allocation of uplink time slots occupied by BW request

When the user equipment needs to send uplink data and there is not enough uplink channel bandwidth, the user equipment will send BW request. There are two ways for user equipment to send BW request. The first is to send in the uplink channel allocated in the current frame; the second is when the user equipment does not allocate an uplink channel in the current frame or the bandwidth allocation of the uplink channel is not enough to send BW request. The device needs to send BW request on the uplink time slot of BW request.

When the BW request is sent in the allocated uplink time slot, according to the existing technology, it only carries a general MAC header and a bandwidth request sub-header. After receiving the BW request, the base station will send a bandwidth permission message to the user equipment through a downlink message , to confirm the received BW request.

The allocation of uplink time slots of BW request is basically similar to the allocation of uplink time slots of UCS, but it is slightly different according to the purpose of BW request.

The base station detects the BW request that may be sent by the user equipment at each sending opportunity of the uplink time slot. On each sending opportunity of the uplink time slot, there may be a BW request, or there may be no BW request, and there may be multiple BW requests. conflict situation. Therefore, for each sending opportunity in the uplink time slot, the processing process of the base station is:

Parse the BW request on every sending opportunity of the uplink slot.

When the BW request can be parsed, add 1 to the set counter (ReceiveValidBWCount) that correctly receives the BW request, and add 1 to the set counter (TotalBWOppCount) that completes a BW request.

When the BW request cannot be resolved, then calculate the power of the data symbols on the transmission opportunity, these data symbols are modulated into the frequency domain of Orthogonal Frequency Division Multiplexing (OFDM), and may span the allocated uplink The data symbol of the time slot, specifically:

其中，k表示数据符号在OFDM调制的子载波位置，而i属于数据符号在OFDM调制的时隙位置。

Among them, k represents the subcarrier position of the data symbol in OFDM modulation, and i belongs to the time slot position of the data symbol in OFDM modulation.

The base station compares the calculated Power with the threshold P1, where the threshold P1 is determined according to the background noise of the WRAN system and the receiving sensitivity of the WRAN system.

If Power is greater than P1, the possible reason is that multiple BW requests sent by different user equipments collide, but it may also be that LU interference occurs on the frequency band where the uplink time slot is located, or a deep decline. Regardless of the reason, handle this situation according to the conflict, that is, add 1 to the counter (ReceiveErrorBWCount) of the set error receiving BW request, and add 1 to TotalBWOppCount;

If Power is not greater than P1, then the reason is that there is no user equipment to send a BW request on this sending opportunity, add 1 to the set counter (ReceiveNullBWCount) that has not received the BW request, and add 1 to the TotalBWOppCount.

In this way, the base station can calculate the receiving performance of the current frame receiving the BW request on the uplink time slot, and this process will be described in detail below.

Use the following formula to calculate the BW request collision rate (BWcollisionRate) of the current frame on the uplink time slot:

BWcollisionRate = ReceiveErrorBWCount/TotalBWOppCount

In addition, in order to make the calculated BWcollisionRate more accurate, the BWcollisionRate of the current frame can be correlated with the BWcollisionRate of the previous frame. If the base station did not adjust the width of the uplink time slot and the size of the backoff window in the previous frame, then the BWcollisionRate of the current frame is calculated as follows:

BWcollisionRate=a*(BWcollisionRate of the previous frame)+(1-a)*ReceiveErrorBWCount/TotalBWOppCount, where a is a fixed coefficient set by the WRAN system, which is between 0 and 1. This a is related to the demand for data smoothing, a The larger the value, the better the smoothing, but the worse the timeliness of data. Conversely, the smaller the value of a, the worse the smoothing, and the better the timeliness of data.

If the calculated BWcollisionRate is greater than the upper limit R1 of the set threshold range, such as 85%, and the R1 is set according to the access control requirements of the WRAN system, then the possible reason is that the BW request is allocated in the uplink time slot of the current frame There are too few sending opportunities, causing collisions between BW requests sent by multiple user equipments in the uplink time slot of the current frame. At this time, the base station can adjust the uplink time slot of the next frame, and the adjustment process is as follows:

Considering that the purpose of the BW request is to apply for the bandwidth of the uplink channel, it needs to be treated differently according to the uplink resources of the current WRAN.

If the allocation of uplink resources of the current WRAN satisfies the business needs of existing user equipment, there is still a large surplus, for example, 30% of the uplink resources of the current WRAN have not been allocated, then the WRAN can serve more users. The device allocates bandwidth, then the base station increases the width of the next frame time slot to accommodate more BW request messages. In addition, it is also possible to increase the sending backoff window for receiving BW request, that is, to set the two parameters of BW request backoff start (Backoff Start) and BW request backoff end (Backoff) End of the sending backoff window for receiving BW request respectively. The change of these two parameters also means that the probability of each user equipment in the selection of the current frame transmission opportunity is reduced, that is, a wider range of transmission opportunities is selected for BW request transmission. Therefore, the present invention alleviates the situation that the uplink time slot of the next frame is not enough for multiple user equipments to send BW request by enlarging the width of the uplink time slot and the size of the sending fallback window.

If the allocation of uplink resources of the current WRAN satisfies the service needs of existing user equipments, there is not much left, such as only 10% of uplink resources, then the base station cannot allocate bandwidth for more user equipments. At this time, the base station cannot adjust the uplink time slot occupied by the BW request, because even if more BW request messages are received, the uplink channel bandwidth cannot be allocated to these user equipments. Therefore, at this time, the Arthur fallback window for receiving BW request can be increased.

If the BWCcollisionRate is less than the lower limit R2 of the threshold range, such as 30%, the WRAN system has met the needs of the current BW request. Considering that the purpose of the BW request is to apply for the bandwidth of the uplink channel, it needs to be treated differently according to the uplink resources of the current WRAN. If the current uplink resource surplus of the WRAN is not much, such as less than 10%, at this time, it may be considered to reduce the occupation of the uplink time slot occupied by the BW request to the entire WRAN, that is, to adjust the width of the uplink time slot occupied by the BW request.

If the current uplink resource surplus of the WRAN is relatively large, such as greater than 30%, the uplink time slot occupied by the BW request does not need to be adjusted at this time, but the size of the sending backoff window is changed to speed up the speed of the user equipment to send the BW request.

After the width of the uplink time slot of the previous frame or several frames is increased and the sending back-off window is increased, the BW request of the uplink time slot of the current frame is still greater than the set R1, so the possible reason is that the uplink time of the current frame The slot channel status is relatively poor, and LU may also interfere with the current WRAN system. Therefore, the present invention needs a solution, and the solution is as follows.

Schedule QP according to the normal process to detect whether there is LU interference on the current communication frequency band. If yes, the frequency band where the uplink time slot is located may be adjusted. For example, the frequency band interfered by the LU is 1 MHz, and the uplink time slot of the current frame is within the first 1 MHz frequency band, then the uplink time slot is adjusted to be within the third 1 MHz partial bandwidth.

Allocation of uplink time slots occupied by Initialization

The purpose of Initialization is to quickly adjust its transmission power to an appropriate range when the user equipment enters the WRAN, and at the same time perform time synchronization with the WRAN network side. It is basically similar to the allocation process of the uplink time slot occupied by UCSNotification, and will not be repeated here. restate.

In addition to adjusting the corresponding uplink time slot according to the state of the above special uplink message during use, other conditions can also be combined as a basis for adjusting the position and size of the corresponding uplink time slot. For example, according to the channel estimation of the WRAN system, it is found that the corresponding uplink time slot is located on a sub-channel with severe frequency selective fading in the frequency domain. Then, the corresponding uplink time slot needs to be adjusted to a subchannel with a good channel state.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. A method for allocating uplink resources, characterized in that the method comprises: The base station calculates the collision rate of the current frame of the specific uplink message sent by multiple user equipments, judges whether the collision rate is not within the set threshold range, and if so, adjusts the uplink time slot or/or the specific uplink message of the next frame and send back-off window, send the adjusted uplink time slot occupied by the specific uplink message and send back-off window information to the user equipment in the next frame through the downlink message, and the user equipment uses the adjusted uplink time slot and send the back-off window information in the next frame One sender within the backoff window sends a specific upstream message. 2. The method according to claim 1, wherein the process of calculating the collision rate of the current frame is: The base station separately counts the error-received specific uplink message counter and the processing completed specific uplink message counter; A. The base station processes the specific uplink message received from the user equipment in each sending opportunity of the uplink time slot occupied by the specific uplink message of the current frame. After the processing is completed, the counter of the specific uplink message is incremented by 1. If the analysis is not obtained Correct specific uplink message, go to step B; B. The base station judges whether the power of the data symbol received at the sending opportunity is greater than the set threshold value, and if so, adds 1 to the wrongly received specific uplink message counter; C. The base station calculates the specific uplink message collision rate according to the error received specific uplink message counter and the processed specific uplink message counter. 3. The method according to claim 2, characterized in that the base station also counts the counter of the specific uplink message correctly received and the counter of the specific uplink message received empty, wherein, In step A, it also includes: if the correct specific uplink message is obtained through parsing, adding 1 to the count of correctly received specific uplink message; In step B, it also includes, if not, adding 1 to the empty received specific uplink message counter. 4. The method according to claim 2, wherein the threshold value in step B is set according to the background noise of the license-free system and the receiving sensitivity of the license-free system. 5. The method according to claim 2, characterized in that the process of calculating the specific uplink message collision rate in step C is: The specific uplink message collision rate is equal to the value obtained by dividing the wrongly received specific uplink message counter by the processed specific uplink message counter. 6. The method according to claim 2, wherein the base station is further provided with a specific uplink message collision rate calculated in the previous frame, and the process of calculating the specific uplink message collision rate in step C is as follows: Specific uplink message collision rate = a × fixed value and specific uplink message collision rate calculated in the previous frame + (1-a) × wrongly received specific uplink message counter/processing completed specific uplink message counter, where a is 0 to 1 Between, fixed coefficients determined by the license-exempt system according to the smoothing requirements of the transmitted data. 7. The method according to claim 1, wherein the threshold range is set according to the load balancing requirement of the license-free system, and is a percentage value. 8. The method according to claim 1, characterized in that the process of adjusting the uplink time slot occupied by the specific uplink message of the next frame or/and sending back-off window is: Judging whether the collision rate is greater than the upper limit of the threshold range, if so, increasing the width of the uplink time slot occupied by the next frame specific uplink message or/and increasing the sending back-off window; Judging whether the collision rate is less than the lower limit of the threshold range, if so, reducing the width of the uplink time slot occupied by the next frame specific uplink message or/and reducing the sending backoff window; According to the scheduled quiet time, it is detected whether there is licensed user interference on the frequency band occupied by the uplink time slot occupied by the specific uplink message or the channel interference or fading value of the frequency band is greater than the set value. The occupied uplink time slot is adjusted to the frequency band where the unlicensed user interference or channel interference is not greater than the set value. 9. The method according to claim 1, wherein the process of adjusting the uplink time slot occupied by the specific uplink message of the next frame or/and sending the backoff window is as follows: C1. Judging whether the conflict rate is greater than the upper limit of the threshold range, if yes, execute step C2; C2. According to the scheduled quiet time, detect whether there is licensed user interference on the frequency band occupied by the uplink time slot occupied by the specific uplink message, or the channel interference or fading value of the frequency band is greater than the set value, and if so, send the next frame specific uplink The uplink time slot occupied by the message is adjusted to the frequency band where the unlicensed user interference or the channel interference of the frequency band is not greater than the set value; if not, then increase the width of the uplink time slot occupied by the next frame specific uplink message Large or/and the send backoff window is increased. 10. The method according to claim 1, wherein the specific uplink message is an initialization message Initialization, a bandwidth resource request message BW request or an emergency coexistence environment notification message UCS Notification.

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