JP3269053B2 - Transmission reservation control method for wireless packet communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission reservation control system for wireless packet communication, and more particularly to a CDM system for a multiple access system.
The present invention is suitable for a wireless packet communication system employing an A (code division multiple access) system and employing a transmission reservation access system as an access system from a terminal to a base station.

[0002]

2. Description of the Related Art In recent years, mobile communication has spread rapidly, and in the past it was only a voice-only service. However, with the spread of the Internet, transmission of higher-speed and larger-capacity media such as data, images, and moving images has been required. And research is being actively conducted to realize it. Packet communication using code division multiple access (CDMA) has attracted attention as a method suitable for multimedia mobile communication that efficiently transmits various media having different properties. The inventor of the present invention has proposed a Slotted CDMA ALOHA Reservation system which adapts ALOHA Reservation system to CDMA as a system for providing a base station and allocating transmission reservation in packet communication using code division multiple access (CDMA). As a technology.

FIG. 13 is a system model diagram of wireless packet communication. In the figure, 51-1 to 51-Nv are voice terminals 1 to Nv, 52-Nv is a multiplier of voice terminal Nv,
Nv is a PN sequence generator of the voice terminal Nv, 54-1 to 54
-Nd is a data terminal 1 to Nd, 55-Nd is a multiplier of the data terminal Nd, 56-Nd is a PN sequence generator of the data terminal Nd, 57 is an equivalent circuit of a combined output, and 58 is a base station. The voice terminals 51-1 to 51-Nv each have a PN
Information input to multipliers 52-1 (not shown) to 52-Nv using assigned unique spreading sequences generated from sequence generators 53-1 (not shown) to 53-Nv Spread the signal directly. Similarly, the data terminal 54-
Multipliers 52-1 (not shown) to 52-52 use assigned unique spreading sequences generated from PN sequence generators 53-1 (not shown) to 53-Nd.
At -Nd, the input information signal is directly spread.
The spread spectrum signals transmitted from the terminals are equivalently added and received by the base station 58 as shown by an equivalent circuit 57 of the combined output.

In this model diagram, Nv voice terminals 51-1 to 51-Nv and Nd data terminals 54-1
1 to 54-Nd wirelessly communicate with one base station (also serving as a radio control station) 58. Even if one terminal device physically functions as both a voice terminal and a data terminal, it is handled as another terminal here. Voice terminal 51-
1 to 51-Nv are terminals that transmit voice packets. During a call, Voice-acti
vation). In the following description, a voice terminal that has detected voice by voice activation and holds a voice packet to be transmitted is called a voice terminal in a voiced state, and other voice terminals are voiceless. It is called the voice terminal in the state. The data terminals 54-1 to 54-N
d has no such distinction.

The voice terminals 51-1 to 51-Nv perform voice coding at intervals of frames (voice coded frames).
The encoded voice is generated in frame units, supplied to the transmission unit, and packetized. The frame length is a fixed length determined by a speech coding method or the like. The transmitting unit transmits a voice packet at the timing of one transmission slot divided in the frame. The voice terminal in the voiced state continuously transmits one voice packet in one frame while the voiced state continues. On the other hand, the data terminals 54-1 to 54-Nd transmit one data packet at random for each frame.

FIG. 14 is a diagram showing a frame configuration of a transmission reservation control method for wireless packet communication according to the prior art. In the figure, a specific example is shown in which the time is taken in the horizontal direction and the channels are arranged in the vertical direction, and the number of channels is 16. This frame configuration
In the uplink from the terminal to the base station. 1
The first period of the frame is a reservation slot for receiving a reservation and is a short period. Subsequent periods are transmission slots for transmitting packets. The downlink uses a different frequency band from the uplink, and a description thereof will be omitted. Also, when applied to a connection-type communication service, a communication phase after a call setting operation has already been completed and a link has been formed,
This transmission reservation control method is applied. Note that the connection establishment operation can also be performed using a reservation slot.

[0007] The transmission reservation control method of the prior art wireless packet communication is based on the voiced state of the voice terminals 51-1 to 51-Nv or the data terminals 54-1 to 54-Nd.
When transmitting a packet, transmission permission (reservation) of the base station 58 is required in advance. Therefore, the base station 58 can control the traffic so as to maintain the communication quality. The length of the voice packet and the data packet is fixed and equal to the length of the transmission slot. A terminal that wants to transmit a packet transmits a reservation request packet having a fixed length equal to the length of the slot to the base station during the reservation slot period. This transmission reservation request packet is also directly spread. Synchronous control, power control, and the like are assumed to be completely performed by respective control processes.

Here, the maximum number of simultaneously transmitted packets that can satisfy the required communication quality is defined as the number of channels. In the case of CDMA, interference between other stations increases as the number of simultaneous transmissions increases. Therefore, transmission of data packets may fail depending on the number of simultaneous transmissions. If transmission fails, retransmission is performed. on the other hand,
For speech, since the redundancy is large, errors are unlikely to be a problem, and other means such as interpolation processing can be used. Therefore, for voice, if the number of simultaneous transmissions of packets is equal to or less than the number of channels described above, it is assumed that voice packet transmission always succeeds.

Next, a reservation control processing method for the audio terminals 51-1 to 51-Nv will be described. First, the voice terminal 5
1-1 to 51-Nv perform voice coding in frame units, and generate one voice packet when voice is detected.
When a packet to be transmitted occurs, a reservation request packet for requesting transmission permission to the base station 58 is transmitted at the timing of the reservation slot. The transmission of the reservation request packet is performed only when the voice packet is transmitted first after the transition to the voiced state in order to prevent an increase in the traffic of the reservation request packet. When the state transitions from the voiced state to the silent state and the reservation is no longer necessary, a reservation release packet for canceling the reservation request is transmitted to the base station.

The base station 58 is connected to each of the voice terminals 51-1 to 51-1.
In response to the reservation request transmitted from -Nv, transmission permission is given to the voice terminal that has requested the reservation within the range of the number of channels per frame. The transmission permission is transmitted to each terminal together with various control signals using the downlink at an arbitrary timing until the beginning of the next frame. After obtaining the transmission permission of the base station 58, the voice terminals 51-1 to 51-Nv that have requested the reservation start transmitting packets from the next frame.

In a certain frame, each voice terminal 51-
If the number of reservation requests from 1 to 51-Nv is equal to or less than the number of channels, the audio terminal 51-1 to 51-Nv that has requested the reservation.
Can send voice packets all in the next frame. However, if the number of reservation requests exceeds the number of channels, the base station 58
The reservation requests of some of the voice terminals 51-1 to 51-Nv are rejected. In the sound state of the audio terminals 51-1 to 51-Nv, one audio packet is continuously generated for each frame. To maintain the immediacy of the voice, the voice packet rejected for transmission is discarded. In addition, in order to maintain fairness among terminals, the selection of the voice terminal rejecting the reservation is performed equally for the voice terminal transmitted in the previous frame and the voice terminal that has newly requested the reservation.

Next, when voice packets and data packets are handled in an integrated manner, in order to transmit voice without discomfort, the immediacy of immediately transmitting voice packets in accordance with the occurrence of encoded voice data is required. Must be guaranteed. On the other hand, data packets must be completely transmitted without errors or omissions even if a delay occurs. Therefore,
The voice packet is prioritized, and the data packet is transmitted when there is a free channel. That is, the data terminal 54
When -1 to 54-Nd generate data packets to be transmitted, they transmit a reservation request packet in a reservation slot.

The base station 58 has voice terminals 51-1 to 51-.
After allocating a reservation to a sound with Nv, if there is a vacant channel, the reservation is also allocated to the data terminals 54-1 to 54-Nd. Data terminal 54- for which no reservation was obtained
The reservation requests of 1 to 54-Nd are reserved until the next frame. When there are reservation requests from a plurality of data terminals 54-1 to 54-Nd, reservations are allocated in the order in which the base station 58 receives reservation request packets. The transmission permission is transmitted to each of the data terminals 54-1 to 54-Nd on the downlink. After transmission, the data packet satisfies the required quality, the success of the transmission is confirmed, and the transmission ends. If transmission fails, retransmission is performed.

In general, voice activation uses voice activation to increase the number of terminals accommodated. Thus, voice traffic is highly time-varying and may temporarily exceed the transmission rate of the system. In that case, in the above-described prior art, the base station 58 restricts transmission of some voice packets in order to avoid packet collision. However, voice calls require immediacy,
Restricted transmissions can result in dropped voice packets,
Communication quality decreases. In order to avoid this, it is sufficient to secure a sufficient margin for fluctuations in voice traffic and line quality. However, there is a problem that the number of terminals that can be accommodated by the system is reduced accordingly.

In a communication system in which voice packets and data packets are integrated, data packets cannot be transmitted if voice packets are simply given priority. The data packet delays transmission because data continuity is required. Therefore, there is a problem that the time required for transmitting the data packet (delay time) is unilaterally degraded during high voice traffic.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a transmission reservation control system for wireless packet communication which increases the number of terminals that can be accommodated. Is what you do. Further, the present invention is a communication system in which wireless packets of different priorities are integrated, even when a higher priority wireless packet is prioritized,
An object of the present invention is to provide a transmission reservation control method for wireless packet communication in which the delay of a wireless packet with a low priority does not deteriorate.

[0017]

According to the present invention, in the first aspect, a reference frame is divided into a plurality of slots, and each of the slots has a plurality of code-multiplexed channels. In response to a request for transmission reservation of a wireless packet from the base station, the base station allocates the slot and the channel to the terminal. The transmission reservation control method for wireless packet communication, which has the same length as the reference frame and Virtual frame determining means for allocating one of the plurality of virtual frames having shifted slots to the terminal that has newly requested the transmission reservation, and that the channel is free for the terminal requesting the transmission reservation. The transmission reservation allocating means for allocating the transmission reservation in the virtual frame allocated to the terminal requesting the transmission reservation. It is intended. That is, since there is a time lag in the virtual frame allocated to the terminal, an allowable delay is secured for each terminal. Therefore, when temporary high traffic exceeding the transmission rate occurs, the virtual device can transmit a virtual reservation beyond the actual terminal capacity by shifting the transmission timing of each terminal to the later slot as far as possible. Therefore, the packet discard rate can be reduced. As a result, the number of terminals that can be accommodated can be increased.

According to a second aspect of the present invention, in the transmission reservation control method for wireless packet communication according to the first aspect, the transmission reservation allocating means sequentially performs the transmission reservation for each of the slots in the reference frame. A transmission reservation is assigned to a transmission reservation non-allocated terminal requesting a transmission reservation in a priority order according to a delay from a leading slot of the virtual frame allocated to the transmission reservation non-allocated terminal. Therefore, it is possible to give as many transmission reservations as possible to the terminal requesting the transmission reservation.

According to the third aspect of the present invention, a reference frame is divided into a plurality of slots, each of the slots has a plurality of code-multiplexed channels, and transmission of radio packets having different priorities from a plurality of terminals. A transmission reservation control method for wireless packet communication in which a base station allocates the slot and the channel to the terminal in response to a request for reservation, wherein a plurality of transmission frames have the same length as the reference frame and are shifted in the first slot. Virtual frame determining means for allocating one of the virtual frames to the terminal transmitting the wireless packet with the higher priority, which has newly requested the transmission reservation, and the high-priority wireless packet requesting the transmission reservation. In the virtual frame allocated to the terminal transmitting the high-priority wireless packet, the transmission reservation A first transmission reservation that preferentially assigns the transmission reservation to at least a part of the terminals that transmit the low-priority wireless packets requesting the transmission reservation as long as the transmission reservation is predicted. Allocating means, for the terminal transmitting the high priority wireless packet requesting the transmission reservation, the virtual frame allocated to the terminal transmitting the high priority wireless packet as long as the channel has a free space; The second transmission reservation allocating means for allocating the transmission reservation within, and, for the rest of the terminals transmitting low priority wireless packets requesting the transmission reservation, as long as the channel has a vacancy, Third for allocating the transmission reservation
Of transmission reservation allocating means. That is, since there is a time lag in the virtual frame allocated to the terminal, an allowable delay is secured for the terminal with a higher priority. Therefore, when temporary high traffic exceeding the transmission speed occurs in a high-priority terminal, the transmission timing of each high-priority terminal is shifted to the later slot as far as possible, so that the priority is increased. A virtual reservation can be given beyond the actual capacity of a terminal having a high priority, so that the packet discard rate of a terminal having a high priority can be reduced. As a result, the number of terminals that can accommodate high-priority terminals can be increased. Also, when allocating transmission reservations, some of the terminals with lower priority have priority over the terminals with higher priority as long as it is predicted that the transmission reservation can be allocated to terminals with higher priority. , It is possible to prevent the one-sided degradation of the packet delay characteristic of the low-priority terminal when the high-priority terminal has high traffic.

According to a fourth aspect of the present invention, in the transmission reservation control method for wireless packet communication according to the third aspect, the second transmission reservation allocating means comprises: In sequence, for a transmission reservation unallocated terminal transmitting the high priority wireless packet requesting the transmission reservation, a priority according to a delay from a head slot of the virtual frame allocated to the transmission reservation unallocated terminal. The transmission reservation is assigned in order. Therefore, it is possible to give as many transmission reservations as possible to a terminal having a high priority requesting the transmission reservation.

According to a fifth aspect of the present invention, in the transmission reservation control method for wireless packet communication according to the third or fourth aspect, the first transmission reservation allocating means is provided for each of the slots in the reference frame. The transmission reservation can be sequentially allocated to the transmission reservation unallocated terminal that transmits the high-priority wireless packet requesting the transmission reservation in the virtual frame allocated to the transmission reservation unallocated terminal. The transmission reservation is preferentially assigned as long as it is predicted. Therefore, it is possible to easily predict whether a transmission reservation can be assigned to a terminal having a high priority.

According to a sixth aspect of the present invention, in the transmission reservation control method for wireless packet communication according to any one of the first to fifth aspects, the virtual frame has the same length as the reference frame. In place of the reference frame, the length of the reference frame is n times as long as the reference frame, and n transmission reservations are allocated in the virtual frame.
Therefore, when the wireless packet communication system allows a delay over a plurality of reference frames, the delay allowance allows the user to enjoy a time margin before discarding the packet, and in addition to this, secures each terminal by a virtual frame. Due to the allowable delay, the superiority of the packet loss rate characteristic can be maintained.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a frame configuration diagram for explaining first and second embodiments of a transmission reservation control system for wireless packet communication according to the present invention. As in FIG. 13, this is composed of a base station and a plurality of terminals, and is used for uplink packet communication from the terminal to the base station. A time is taken in the horizontal direction and a code multiplex channel is arranged in the vertical direction. In the prior art,
In contrast to a speech coded frame which is composed of one reservation slot and one transmission slot, in this embodiment, one frame is composed of one reservation slot and four transmission slots. The length of each slot is equal to the reservation packet length and the transmission packet length. The length of each slot is determined according to the specific communication system.
The time length of one slot is reduced to 1/4. As a result, the number of channels is reduced to 1/4 of that of the prior art because the spread spectrum rate is reduced to 1/4. The “frame” of the base station is hereinafter referred to as a “reference frame” to distinguish it from a virtual frame described later. The voice coding of all voice terminals is performed in units of the reference frame length, and the voice coded signal is input to the transmission unit.

Each voice terminal has a virtual frame in addition to the reference frame. The virtual frame has the same length as the reference frame, and the leading slot is shifted. For example, in the figure, the 0th virtual frame has the 0th transmission slot at the top, and the 1st virtual frame has the 1st transmission slot at the top. One of a plurality of virtual frames is allocated by the base station to the voice terminal that has newly requested transmission reservation. Note that the data terminal does not have the concept of the virtual frame, and always follows the reference frame.

FIG. 2 is a flowchart for explaining the processing of the first embodiment of the transmission reservation control method for wireless packet communication according to the present invention. The first embodiment of the present invention is based on a wireless packet communication system using only voice packets or a transmission reservation control method that focuses only on voice terminals in wireless packet communication that handles voice packets and data packets in an integrated manner. And

In step S11, the voice terminal transmits a reservation request packet for requesting transmission reservation of a wireless packet.
In S21, the base station receives a reservation request packet and a later-described reservation release packet in the first reservation slot of each reference frame. The base station performs S22
, A virtual frame is allocated to the voice terminal for which a new reservation request has been made. Alternatively, the virtual frame of the voice terminal whose reservation has been released is released. In S23, as long as there is a free channel, the reservation is assigned to one channel of one slot in a virtual frame allocated to the voice terminal requesting the reservation. By performing reservation allocation in a virtual frame, an allowable delay can be ensured as compared with the prior art. This is possible only if the audio packets are at intervals of audio encoding (in frame units).
This is because it occurs in. However, in this specific example, the processing itself of the base station performs transmission reservation processing in units of reference frames. In step S24, the base station transmits a transmission permission signal designating the slot and channel to which the reservation has been assigned to the voice terminal, and ends the processing of one reference frame. In the illustrated example, not only the transmission permission signal but also the transmission non-permission signal is not transmitted to the voice terminal to which no reservation is assigned.

In step S12, the voice terminal determines whether or not the transmission permission signal has been received. If the signal has not been received, the process proceeds to step S13.
The process proceeds to S4, the voice packet is discarded, and the process proceeds to S15. In S13, the voice packet is transmitted on the designated channel of the transmission slot designated by the base station, and the process proceeds to S15. In S15, it is determined whether or not a silent state of the voice is detected, and if no silent state is detected, the process returns to S12. When a silent state is detected, the process proceeds to S16, a reservation release packet is transmitted in the transmission reservation slot of the next reference frame, and in S17 to S19, the last voice packet is transmitted, and the transmission of a continuous voice packet is performed. finish.

FIGS. 3 to 5 are frame configuration diagrams for specifically explaining the processing of the first embodiment of the transmission reservation control method for wireless packet communication according to the present invention. In the extreme state where all channels are occupied by voice terminals, a case where a new transmission request packet is received is shown. 3 is a diagram showing a frame configuration at the end of the first reference frame, FIG. 4 is a frame configuration diagram at the end of the second reference frame, and FIG. 5 is a frame configuration diagram at the end of the third reference frame.

In FIG. 3, the first to third transmission slots of the first reference frame and the first to third channels thereof all have the first to third virtual frames. It is assigned to the assigned voice terminal. Immediately after a certain voice terminal transits from a silent state to a sound state, the voice terminal sends a reservation request packet in a reservation slot. Upon receiving the reservation request packet, the base station determines the reservation allocation of the transmission slot in the next second reference frame within the first reference frame period, and makes a reservation using a downlink channel (not shown). A transmission permission signal for designating the transmission slot number and the channel number to be used is transmitted to the terminal to be assigned.

In FIG. 4, the voice terminal that has transmitted the reservation request packet receives the 0th frame in the second reference frame.
It is assumed that the first channel of the transmission slot is allocated. The transmission slot allocated first is defined as a reference slot. Therefore, the 0th
The second transmission slot is a reference slot, and this voice terminal has been allocated virtual frame 0. Each voice terminal has a virtual frame whose length is the same as the length of the reference frame, starting from the reference slot. The reference slot is determined in the base station such that the distribution of the reference slot allocated to each voice terminal is uniform in the reference frame. A transmission slot and a channel for transmitting a packet are designated by the base station for each reference frame, and are designated to each terminal using a downlink channel (not shown) in the immediately preceding reference frame. The determination of the transmission slot is performed so that each voice terminal is equally close to the first reference slot of the virtual frame as much as possible. Each voice terminal has a virtual frame assigned to each voice terminal.
The voice packet is transmitted on the designated channel of the transmission slot designated by the base station.

In the illustrated example, since the channel is not vacant, the voice terminals of virtual frames 0 to 2 using the 0th to 3rd transmission slots of the 1st channel are In the reference frame, the transmission slot is shifted backward by one slot. One voice terminal to which the third virtual frame using the third transmission slot has been allocated has no transmission slot allocated in the second reference frame, and
The transmission slot of the reference frame is virtually reserved. Since the transmission slot is equally allocated to the voiced voice terminal, the voice terminal that has transmitted the reservation request packet in FIG. 3 may not be allocated for reservation in the second reference frame.

In FIG. 5, the voice terminal that transmitted the reservation request packet in FIG. 3 indicates that the second channel of the 0th transmission slot, which is the reference slot, was also allocated in the third reference frame. I do. On the other hand, the voice packet virtually reserved in FIG.
It is assumed that the first channel of the 0th transmission slot is allocated. As a result, the voice terminal using the second channel of the third transmission slot in the second reference frame of FIG. 4 has the transmission slot of the third reference frame. Not allocated and virtually reserved for the next reference frame. Also, the voice terminal that has been virtually reserved in FIG. 4 is not assigned a transmission slot for the next voice packet in this third reference frame, and is virtually reserved again for the next reference frame.

In FIG. 4, the voice terminal which has not been allocated in the second reference frame and has been virtually reserved is used in the third reference frame in the first transmission slot of the 0th transmission slot shown in FIG. To the th channel, etc.
Not always. Naturally, the priority of allocation is higher, but there are cases where the allocation is not performed due to a priority relationship with other voice packets or lottery. In the above description, an example is shown in which only the transmission slot is shifted, but the channel number may be changed at the same time.

Also in the above-described embodiment, as in the prior art, the voice terminal in the sound state generates one voice packet continuously for each frame, so that the transmission reservation is made within the virtual frame of each voice terminal. If not, the voice packet is discarded to maintain immediacy. However, by introducing a plurality of slots and a virtual frame, even if the voice terminal transmits a voice packet that must be transmitted at least once in one reference slot in the last transmission slot of the virtual frame, the voice packet is discarded. No longer occurs. In other words, even if the voice traffic of a certain reference frame temporarily exceeds the capacity of the reference frame (in the illustrated example, a total of 16 channels), the reservation of some voice terminals is changed to the next reference frame. By postponing, it is possible to avoid rejection of a reservation that leads to discard of a voice packet.

A voice terminal whose reservation has been postponed to the next reference frame can also obtain a reservation in its own virtual frame.
Voice packets are not dropped. However, since there is no guarantee that a reservation can be obtained in the next reference frame, it is called a virtual reservation. Even if a virtual reservation is made, the number of transmission channels does not increase, so if voice traffic continues to exceed the number of channels for a long time, voice packets will eventually be discarded. However, if the overload state is resolved before that, the voice packet will not be discarded, and if any terminal transitions from the voiced state to the silent state and the transmission channel becomes free, the delay will be eliminated. Return to the original state.

FIG. 6 is a frame configuration diagram for introducing a general formula into the processing of the first embodiment of the transmission reservation control method for wireless packet communication according to the present invention. Here, it is assumed that one reference frame is composed of M transmission slots, and the 0th to M−1
The number k is given to the number. K + of the previous reference frame
A virtual frame whose first transmission slot is a reference slot starts from this (k + 1) th transmission slot,
The reference frame ends at the k-th transmission slot.
A virtual frame in which the (k + 2) th transmission slot of the immediately preceding reference frame is the reference slot starts from the (k + 2) th transmission slot and ends with the (k + 1) th transmission slot of the reference frame. Similarly, a virtual frame in which the (k-1) -th transmission slot of this reference frame is a reference slot starts from the (k-1) -th transmission slot and starts at the (k-2) -th transmission slot of the next reference frame. end with. A virtual frame in which the k-th transmission slot of the reference frame is a reference slot starts from the k-th transmission slot and starts at k of the next reference frame.
Ends at the first transmission slot.

The reservation allocation process is performed on a reference frame basis. The base station allocates reservations in order from the first 0th transmission slot based on the reservation request packet and reservation release packet received in the reservation slot at the head of the reference frame and the previous reservation status. In the following, focusing on the k-th transmission slot, it is assumed that the reservation allocation of the (k-1) -th transmission slot has been completed, and a method of allocating the reservation to the k-th transmission slot will be described.

The base station includes, from among the voice terminals requesting the reservation, the transmission slot of interest in the virtual frame, and the voice terminal for which the reservation has not yet been obtained in the virtual frame. , A voice terminal having a long waiting time from the reference slot is prioritized, and a reservation is allocated within an allowable range of the number of channels. At this time, the priority of the voice terminal having the (k + 1) th transmission slot next to the transmission slot of interest as the reference slot is the highest. If no reservation is assigned to this voice terminal, the voice packet of this voice terminal is discarded because the voice packet cannot be transmitted within one virtual frame period.

Next to the transmission slot of interest, k +
The voice terminal using the second transmission slot as a reference slot has the next highest priority. The voice terminal may transmit the voice packet up to the (k + 1) th transmission slot. As you can see, the priority of reservations gradually decreases,
The voice terminal whose reference slot is k has the lowest priority.
Voice terminals are assigned to empty channels in order of priority, and terminals with the same priority are equally selected by lottery. If the above reservation allocation method is performed from the first transmission slot 0 of the reference frame to the last (M-1) th transmission slot, the reservation allocation of the reference frame is completed. The voice terminal to which the reservation is assigned transmits a voice packet on the designated channel of the reserved transmission slot of the next reference frame.

Next, a second embodiment of the transmission reservation control method for wireless packet communication according to the present invention will be described. The second embodiment is applied to a wireless packet communication system that handles voice packets and data packets in an integrated manner. Earlier, the frame structure shown in FIG. 1 has the ability for voice terminals to withstand temporary high traffic. By utilizing this fact, a part of the data packet is reserved (priority reservation) prior to the voice packet. After the priority reservation is made, the reservation of the voice terminal is made for the remaining channels in the same manner as in the first embodiment, and the reservation of the data packet of the remaining data terminal is made for the last remaining channel. Do. That is, the priority of the data packet is partially higher than that of the voice packet as compared with the first embodiment.

FIG. 7 is a flowchart for explaining the processing of the second embodiment of the transmission reservation control method for wireless packet communication according to the present invention. The packet transmission process in the voice terminal is the same as that in the first embodiment shown in S11 to S19 in FIG. In S31 on the data terminal side, a reservation request packet is transmitted. Except for voice data, data generally does not occur continuously over a long period of time. Also, at the time of sending the reservation request packet, the data amount is known in advance,
In many cases, the number of packets can be calculated. Therefore, when transmitting the reservation request packet, the number of packets is notified. Of course, a reservation request packet may be transmitted every time there is a data transmission request. In either case,
No reservation request release packet is required.

The base station receives the reservation request packet and the reservation release packet as in S21 of FIG. In S42, as in S22 of FIG. 2, a virtual frame is allocated to the voice terminal that has newly requested the reservation, and the virtual frame of the voice terminal whose reservation has been released is released.
In S43, a priority reservation is assigned to a part of the reserved data terminals for each reference frame. When determining the number of priority reservations, it is necessary to consider virtual reservations for voice terminals. For the voice terminal requesting the reservation, the data for which the reservation is being requested, as long as the reservation can be assigned to one channel of one transmission slot in the virtual frame allocated to the voice terminal. A reservation is preferentially assigned to at least a part of the terminal. As will be described later in more detail, it is predicted that, for each slot in the reference frame, a reservation can be sequentially allocated to an unallocated voice terminal that is requesting a reservation in a virtual frame allocated to this voice terminal. As far as possible, the transmission reservation is preferentially assigned.

In S44, similarly to S23 in FIG. 2, the reservation is allocated in the virtual frame of the voice terminal that is making the reservation. In S45, the reservation is allocated to the remaining data terminals being reserved for each reference frame as long as the channel has a free space. In S46, as in S24 of FIG. 2, a transmission permission signal with a transmission slot and channel designation is transmitted.

In S32 on the data terminal side, it is determined whether or not a transmission permission signal has been received.
The process proceeds to S33, and if not received, the process proceeds to S34. In S33, the data packet is transmitted on the designated channel of the designated transmission slot, and the process proceeds to S35. In S34, the process waits for the transmission of the data packet, reserves it, and proceeds to S35. In S35, it is determined whether or not the transmission of the predetermined number of data packets has been completed. If the transmission has not been completed, the process returns to S32,
When the transmission is completed, the process ends. In the above description, description of processes such as retransmission control when an error occurs is omitted. Further, when transmitting a data packet from one data terminal, if only one data packet can be transmitted within one reference frame, the system is simplified. However, the system may be capable of transmitting a plurality of data packets within one reference frame.

Referring again to FIG. 6, the determination of the number of priority reservations in S43 will be described in detail. It is assumed that the reservation allocation of the (k-1) th transmission slot has already been completed on the assumption that there is no change in the number of voiced voice terminals during one frame period up to the next reference frame. ,
Focusing on the kth (0 <k <M-1) th transmission reserved slot, the priority reservation number _Yk is derived.

If a voice terminal having the (k + 1) -th transmission slot as a reference slot has not yet been assigned a reservation by the (k-1) -th transmission slot, the reservation is made in the k-th transmission slot. If not, the voice packet is discarded. To avoid this, the priority reservation number of data packets in the k-th transmission slot is

(Equation 1) Must be: C is the number of channels per slot, X _k (i) has the (k + i) -th transmission slot as a reference slot, and the k-th transmission slot is included in the virtual frame. Define the reservation as the number of unassigned voice terminals.
Here, in the mathematical expression, if k + i exceeds M-1, the reference frame exceeds the reference frame of interest and reaches the next reference frame. Therefore, the corresponding slot number is k + i.
mod M.

Next, if a voice terminal having the (k + 2) th transmission slot as a reference slot has not yet been assigned a reservation, the reservation is made in the kth transmission slot or the next (k + 1) th transmission slot. If not assigned, the voice packet is discarded. Therefore, the priority reservation number of the k-th slot is

(Equation 2) The following condition must be satisfied at the same time. In this way, the priority reservation number Y _k of the data packet when considering the voice terminal having the k-th slot as the reference slot is

[0048]

(Equation 3) Must. Here, the symbol min (•) is the minimum value in parentheses when i is a positive integer from 1 to M.

A value obtained by multiplying this by a parameter β (0 ≦ β ≦ 1) representing the priority of the data with respect to the voice is defined as a data packet priority reservation number Y _k of the k-th slot.

(Equation 4) In this way, the data terminal is preferentially reserved for each of the reference slots 0 to M-1 of the reference frame.

FIG. 8 is an explanatory diagram of a specific example of the priority reservation of the data terminal when the number M of transmission slots is set to four.
First, a priority reservation of the data terminal in the 0th transmission slot is made. (1) The total number to which the voice terminal of the virtual frame 1 has not yet been assigned a reservation is X ₀ (1). A reservation must be allocated to this voice terminal in the 0th transmission slot of interest. Therefore, when only the reservation allocation of the voice terminal of the virtual frame 1 is considered, the priority reservation number of the data terminal that can be allocated in the 0th transmission slot is:

(Equation 5) Must be:

(2) The total number to which the voice terminal of the virtual frame 2 has not yet been assigned a reservation is X ₀ (2). A reservation must be assigned to this voice terminal in the 0th transmission slot of interest or the next 1st transmission slot. Therefore, when considering up to reservation allocation to the first transmission slot in advance, the number of preferential reservations of data terminals that can be allocated in the zeroth transmission slot is as follows:

(Equation 6) Must be:

(3) The total number to which the voice terminal of the virtual frame 3 has not yet been assigned a reservation is X ₀ (3). A reservation must be allocated to this voice terminal from the 0th to the 2nd transmission slot of interest. Therefore, when considering up to reservation allocation to the second transmission slot in advance, the priority reservation number of data terminals that can be allocated in the zeroth transmission slot is:

(Equation 7) Must be:

(4) The total number to which the voice terminal of virtual frame 0 has not yet been assigned a reservation is X ₀ (0). This voice terminal must be able to allocate a reservation from the 0th to the 3rd transmission slot of interest. Therefore, when considering beforehand the reservation allocation of the voice terminal to the third transmission slot, the priority reservation number of the data terminal that can be allocated in the zeroth transmission slot is:

(Equation 8) Must be:

(5) Of the above four cases, the one with the least number of priority reservations of the data terminal is assigned to the data terminal in any case within the limit that it is not necessary to assume that the voice packet is discarded. This is the maximum number of channels that can be reserved by priority. Therefore, finally, the priority reservation number of the data terminal in the 0th transmission slot of interest is given by taking the above-mentioned count β into consideration.

(Equation 9) Becomes As a result, in the 0th transmission slot, the number of channels allocated to voice packets is reduced by the number of data packets that have been reserved for priority, and the number of channels assigned to voice terminals to which no reservation has been allocated by the end of the 0th transmission slot. The number will increase.

Next, the transmission slot of interest is set to 1
Then, the priority reservation of the data terminal is performed for the first transmission slot. Priority reservation method, the method described above,
Since the transmission slot is only advanced by one, the description is omitted. In this way, the priority reservation of the data terminal can be made for all the transmission slots.

In the above description, a case has been described in which the system allows a delay over one frame for a voice packet. However, in some systems, multiple n
In some cases, delays over frames may be tolerated. In the prior art described above, the same is true. When a delay of n frames is allowed, in the prior art, when a voice packet cannot be transmitted, the voice packet is not immediately discarded, but held on the transmitting side for n frames. Wait until transmission is possible. That is, there is a margin of n frames until the packet is discarded. In the meantime, it is sufficient to wait until the traffic decreases and the transmission slot becomes free. On the other hand, while there are voice packets waiting to be transmitted,
Wait without being sent.

On the other hand, when the delay of n frames is allowed in the embodiment of the present invention, the time limit before discarding is extended to n frames, and as a result, the length of the virtual frame is reduced to the reference frame. , But the method of packet reservation is basically the same. However, since one encoded voice is output in units of the reference frame length, n transmission reservations of voice packets are allocated in one virtual frame. Regarding the priority of voice packet reservation, among voice terminals that have not been reserved yet, the time to be transmitted originally, that is,
A voice terminal having a long time delay from the reference slot, which is the transmission slot at the head of the virtual frame, is given priority. Therefore, as a result of the time limit until the packet is discarded being extended by n frames, the time margin before the packet discarded by the prior art can be similarly enjoyed in the embodiment of the present invention. Can be. In addition to this, it is possible to enjoy the superiority of the packet loss rate characteristic obtained by using the virtual frame. On the other hand, as in the case of the voice terminal allowing one frame delay, a part of the data packet is preferentially reserved over the voice packet, and the rest wait until the delay of the voice packet is eliminated.

One frame is composed of M slots,
In the case where a delay of up to n frames is allowed for the voice terminal, the number of data packet priority reservations of a certain k-th transmission slot to be focused on is as follows.

(Equation 10) In other words, the expression is not different from the expression (2). Where X
_k (l) represents the number of voice terminals that become l (lowercase letter L) when the remaining time limit until the discarded slot is expressed in units of slots in voice packets waiting for transmission. Also
min (·) is the minimum value in parentheses when i is a positive integer from 1 to M · n (the total number of slots in the virtual frame).

Finally, the results of computer simulation performed on the first and second embodiments will be described. In the simulation, Nv shown in FIG.
It is assumed that there are no voice terminals and Nd data terminals connected to the base station, and there is no change in the number of connected terminals due to the occurrence and disappearance of a call. All voice terminals are
It is assumed that voice activation has been performed.

FIG. 9 is a state transition diagram of the voice terminal used for the simulation. All voice terminals transition to either a silent state or a sound state in units of reference frames. The voice terminal in the silent state transits to the voiced state with probability λ,
Stay silent at λ. The voice terminal in the voice state transitions to the silence state with the probability μ, and stays in the voice state with 1−μ.

The state transition probability λ is obtained from the average silence time of the voice terminal and the reference frame length, and is expressed by the following equation.

[Equation 11] The state transition probability μ is obtained from the average sound duration of the voice terminal and the reference frame length, and is expressed by the following equation.

(Equation 12) A voice terminal in a voiced state generates a voice packet for each reference frame. On the other hand, there is no state transition in the data terminal, and one data packet is generated for each reference frame according to the data packet occurrence probability α. However, it is assumed that no new data packet is generated during the transmission standby time from the transmission of the reservation request packet to the actual transmission of the data packet.

Table 1 shows the specifications of the simulation. However, it is assumed that transmission power control is completely performed without considering interference from other cells. Therefore, it is assumed that the packet transmission always succeeds when the number of simultaneous transmissions of the packet is equal to or less than the number of channels. Also, transmission errors and propagation delays of reservation request packets and control signals are not considered.

[0063]

[Table 1] Since the priority reservation number Y _k of the data terminal is obtained as a real number,
In actual use, it must be an integer. In order to accurately reflect the effect of the parameter β, the decimal part is set to the probability of being carried up to an integer each time it is used. For example, if Y _k is 1.2, it becomes 2 with a probability of 20%, and 80%
Is 1 with the probability of

The performance evaluation of the system is performed by comparing the discard rate of voice packets with the average delay time of data packets. Voice offered load G _v representing the traffic of voice terminals, it is defined by the following equation.

(Equation 13) Here, N _v : number of voice terminals λ: state transition probability from silence state to speech state μ: state transition probability from speech state to silence state C: number of channels per slot M: transmission per frame The number of slots.

Note that λ / (λ + μ) is a voice activity coefficient.

[Equation 14] be equivalent to.

The data offered load representing the traffic of the data terminal is defined by the following equation.

(Equation 15) Here, N _d : number of data terminals α: data packet occurrence probability C: number of channels per slot M: number of transmission slots per frame

For comparison, the number of packets per frame in the prior art and the new system according to the embodiment of the present invention is assumed to be the same, so that the number of slots M per frame in the prior art and the new system is 1 Table 2 shows the number of channels C per slot.

[Table 2] The voice packet discard rate is given by the ratio of the number of voice packets discarded to the number of generated voice packets. The average delay time of a data packet is the average of the number of successfully transmitted data packets measured from the reference frame following the transmission of the reservation request packet by the data terminal until the transmission is completed in frame units. .

To compare the voice packet discard rate characteristics,
The simulation was performed assuming that there is no data terminal. FIG. 10 is a diagram showing voice packet discard rate characteristics. It can be seen that the new system has superior discard rate characteristics compared to the prior art. Table 3 shows the results of a quantitative comparison using the maximum offered load that can satisfy the specified discard rate.

[Table 3] The drop rates in Table 3 represent the drop rates that the system must satisfy in voice packet transmission, and the conventional scheme and the new scheme indicate the maximum offered load that satisfies the specified voice packet drop rates. The improvement is the increase in offered load resulting from the ratio of the new method to the prior art. Since the offered load increases when the discard rate and the number of packets accommodated in the frame are the same, it can be seen that the new system increases the number of terminals that can be accommodated.

In order to evaluate the average delay time characteristic of the data packet and the voice packet loss rate characteristic when a data terminal is present, the number of voice terminals was fixed to 80 and the simulation was performed while changing the number of data terminals. FIG. 11 is a diagram illustrating an average delay time characteristic of a data packet with respect to an offered load of a data terminal. β is the priority of the data packet with respect to the voice packet. FIG. 12 is a diagram illustrating a voice packet loss rate characteristic with respect to offered load of a data terminal. Note that the entire offered load that participates in the system is the offered load G of the data terminal.
a plus offered load G _v of the voice terminal _d. In this case, the expected value of the voice offered load G _v is approximately
0.854.

In FIG. 11, except for β = 0.025, the transmission of data packets is completed in a shorter time than in the prior art, and it can be seen that the new method has improved the average delay time characteristics of data packets. . The improvement effect is greatest when β = 1, and the improvement effect decreases as β decreases. When β = 0.025, the priority is reversed in the area where the offered load G _{d of} data is 0.07 or more, but this is because the priority for data packets is too low, and the improvement of the discard rate of voice packets has priority. It is thought that it was done.

In FIG. 12, the characteristic when the offered load G _d of the data terminal is 0 is the characteristic shown in FIG. 10 evaluated only with the voice packet (the voice offered load G _v is 0.854).
Matches. Discard rate characteristic of the prior art, certain Nanoha against offered load G _d of the data, the prior art reservation control method, considered from simply prioritize voice packets. The influence of the new scheme is preferentially reserved, according to offered load G _d of the data packet increases, the voice packet discard rate characteristic deteriorates, worse than Eventually prior art by beta.

There is a trade-off between the average delay time characteristic of the data packet shown in FIG. 11 and the voice packet loss rate characteristic shown in FIG. Which is given priority is determined by β. If β is increased and the data terminal is prioritized as in β = 1, the average delay time characteristic of the data packet is greatly improved, but the voice packet discard rate characteristic increases the offered load G _d of the data packet. , And eventually worse than the prior art. Conversely, if β is reduced with priority given to the voice terminal such as β = 0.025, the voice packet discard rate characteristics will always be better than the prior art, but the effect of improving the average delay time characteristics of data packets will be small. becomes, if increasing offered load G _d of the data packets, worse than before long the prior art. At β = 0.05, the voice packet discard rate characteristics are superior to or worse than those of the prior art and are almost the same, and the average delay time characteristics of the data packets are improved. Therefore, the optimum β may be determined according to the required quality of voice and data determined by the system.

In the above description, the reserved slot is provided once for one reference frame. Alternatively, the reserved slot may be provided once in a plurality of reference frames. In this case, the reservation request and the reservation release can be made once for a plurality of reference frames. In the above description, the reservation request packet and the reservation release packet are transmitted using the same frequency band as the voice packet and the data packet, but may be transmitted using another frequency band. In the above description, the case where two types of packets, that is, a voice packet and a general data packet, are integrated to perform packet communication has been exemplified. However, the above-mentioned voice packet is only a typical example of a packet required to maintain immediacy. Voice activation has a remarkable effect when accompanied by voice activation, but is not essential. Media that needs to maintain immediacy include voice as well as videophones,
There is image data for videoconferencing, surveillance cameras, etc. Suppressing the rate at which packets transmitting these media are discarded while maintaining immediacy as much as possible leads to improvement in service quality. On the other hand, since general data is used after being stored on the receiving side, immediacy is not required, but rather, continuity without data error or data omission is required. For packets transmitting media requiring continuity, maintaining continuity and suppressing transmission delay as much as possible leads to improvement in service quality.

As is clear from the above description,
The embodiment of the transmission reservation control method for wireless packet communication according to the present invention has a configuration in which two types of packets having different characteristics, that is, a voice packet and a data packet, have a difference in transmission reservation priority. Therefore, with such a configuration,
The wireless packet communication transmission reservation control method of the present invention can be applied to a wireless packet communication system in which it is preferable that the priorities of transmission reservations be different. Further, the transmission reservation control method of wireless packet communication according to the present invention is applicable to any of a wireless packet communication system in which a terminal is a mobile terminal and a wireless LAN system in which a terminal does not always move. Note that the technical concept of the transmission reservation control method for wireless packet communication of the present invention can be applied to wireless packet communication having a plurality of channels in which a reference frame is divided into a plurality of slots and each slot is frequency-multiplexed.

[0075]

As described above, the transmission reservation control method for wireless packet communication according to the present invention has an effect that the number of terminals that can be accommodated can be increased. For example, even if the number of voice terminals temporarily exceeds the capacity per frame due to the use of voice activity, etc., virtual frames are used to avoid discarding voice packets and relatively increase the capacity of the system to accommodate terminals. There is an effect of improving. Also, in a communication system in which packets with different priorities are integrated, when a packet of a terminal with a higher priority is given priority,
There is an effect that the delay of the packet of the terminal with low priority does not deteriorate. For example, during high traffic traffic on voice terminals,
By simply preventing the characteristics of the data terminal from deteriorating, there is an effect that quality control (QoS) between media becomes possible.

[Brief description of the drawings]

FIG. 1 is a frame configuration diagram for explaining first and second embodiments of a transmission reservation control method for wireless packet communication according to the present invention.

FIG. 2 is a flowchart illustrating a process of a first embodiment of a transmission reservation control method for wireless packet communication according to the present invention.

FIG. 3 is a diagram illustrating a frame configuration at the end of a first reference frame.

FIG. 4 is a diagram illustrating a frame configuration at the end of a second reference frame.

FIG. 5 is a diagram illustrating a frame configuration at the end of a third reference frame.

FIG. 6 is a frame configuration diagram for introducing a general formula into the processing of the first embodiment of the transmission reservation control method for wireless packet communication according to the present invention.

FIG. 7 is a flowchart illustrating a process according to a second embodiment of the transmission reservation control method for wireless packet communication according to the present invention.

FIG. 8 is an explanatory diagram of a specific example of priority reservation of a data terminal when the number of transmission slots is four.

FIG. 9 is a state transition diagram of a voice terminal used for simulation.

FIG. 10 is a diagram showing a voice packet loss rate characteristic for offered load of a voice terminal.

FIG. 11 is a diagram illustrating an average delay time characteristic of a data packet with respect to an offered load of a data terminal.

FIG. 12 is a diagram illustrating a voice packet loss rate characteristic with respect to an offered load of a data terminal.

FIG. 13 is a system model diagram of wireless packet communication.

FIG. 14 is a frame configuration diagram of a transmission reservation control method for wireless packet communication according to the prior art.

[Explanation of symbols]

51-1 to 51-Nv Voice terminals 1 to Nv, 52-Nv
Multiplier of voice terminal Nv, 53-Nv PN sequence generator of voice terminal Nv, 54-1 to 54-Nd Data terminal 1
~ Nd, 55-Nd Multiplier of data terminal Nd, 56-
Nd PN sequence generator for data terminal Nd, 57 Equivalent circuit of combined output, 58 Base station

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/28 H04Q ^7/ 00-7/38 H04B ⁷ /24-7/26

Claims (6)

(57) [Claims] 1. A reference frame is divided into a plurality of slots, and each slot has a plurality of code-multiplexed channels. In response to a request for transmission reservation of a wireless packet from a plurality of terminals, a base station transmits the plurality of channels to the terminal. A transmission reservation control method for wireless packet communication that allocates the slot and the channel, wherein one of a plurality of virtual frames having the same length as the reference frame but shifted from the first slot is newly assigned to the transmission reservation Virtual frame determining means for allocating to the terminal that has requested the transmission request, and for the terminal that is requesting the transmission reservation, the virtual frame allocated to the terminal that is requesting the transmission reservation as long as the channel has a free space. A transmission reservation allocating means for allocating the transmission reservation within the transmission reservation control method for wireless packet communication. 2. The transmission reservation allocating means sequentially allocates the transmission reservation unallocated terminals to the transmission reservation unallocated terminals requesting the transmission reservation for each of the slots in the reference frame. The transmission reservation control method for wireless packet communication according to claim 1, wherein the transmission reservation is assigned in a priority order according to a delay from a leading slot of the virtual frame. 3. A reference frame is divided into a plurality of slots, each of the slots has a plurality of code-multiplexed channels, and a base station responds to a request from a plurality of terminals for transmission reservation of wireless packets of different priorities. A transmission reservation control method for wireless packet communication in which a station allocates the slot and the channel to the terminal, wherein one of a plurality of virtual frames having the same length as the reference frame and a shifted leading slot is added to the new frame. Requesting the transmission reservation to, virtual frame determining means to allocate to the terminal transmitting the high-priority wireless packet, for the terminal transmitting the high-priority wireless packet requesting the transmission reservation, As long as it is predicted that the transmission reservation can be assigned in the virtual frame allocated to the terminal transmitting the high-priority wireless packet. Stomach,
A first transmission reservation allocating unit that preferentially allocates the transmission reservation to at least a part of the terminals that transmit the low-priority wireless packets requesting the transmission reservation; For a terminal that transmits a high-priority wireless packet, a second allocation of the transmission reservation in the virtual frame allocated to the terminal that transmits the high-priority wireless packet, as long as the channel is vacant. Transmission reservation allocating means, and a third transmission reservation for allocating the transmission reservation to the rest of the terminals transmitting low-priority wireless packets requesting the transmission reservation as long as the channel is free. A transmission reservation control method for wireless packet communication, comprising: allocating means. 4. The transmission reservation non-allocation terminal for sequentially transmitting the high-priority wireless packets requesting the transmission reservation for each slot in the reference frame, wherein the second transmission reservation allocating means is provided for each slot in the reference frame. 4. The wireless packet according to claim 3, wherein the transmission reservation is allocated in a priority order according to a delay from a head slot of the virtual frame allocated to the terminal to which the transmission reservation has not been allocated. 5. Transmission transmission reservation control method. 5. The transmission reservation non-allocation terminal for sequentially transmitting the high-priority wireless packets requesting the transmission reservation for each slot in the reference frame, wherein the first transmission reservation allocating means is provided for each slot in the reference frame. The transmission reservation is preferentially allocated as long as it is predicted that the transmission reservation can be allocated in the virtual frame allocated to the transmission reservation unallocated terminal. 3. The transmission reservation control method for wireless packet communication according to 3 or 4. 6. The virtual frame has a length equal to a plurality of n times the reference frame instead of having the same length as the reference frame, and n transmission reservations are allocated in the virtual frame. The transmission reservation control method for wireless packet communication according to any one of claims 1 to 5, wherein: