KR100381768B1 - Medium Access Control Protocol for Dynamic Resource Allocation in the Wireless ATM Networks - Google Patents

Abstract

The present invention relates to a communication protocol of a dynamic resource allocation method for a medium access control protocol capable of efficiently utilizing limited wireless bandwidth in a wireless ATM environment and ensuring quality of service for various traffic classes.

Since the existing wireless medium access control protocol cannot effectively support the characteristics of average cell rate and maximum cell rate for variable bit rate traffic, cell loss problem is severe in variable bit rate acceptance method considering average cell rate and maximum cell rate. In the variable bit rate accommodating method in which the fixed bandwidth is allocated, the bandwidth usage efficiency is low due to the unused slots.

According to the present invention, dynamic reservation can be performed on a frame-by-frame basis in consideration of the simplification of slot allocation implementation and the guarantee of service quality at the same time, and can be processed in real time based on priority. It can increase. In addition, for effective bit rate traffic, the minimum effective bit rate bandwidth is set to improve the delay and network throughput according to the slot contention scheme for access in the uplink, and the bandwidth of the mobile terminal's traffic occurrence rate and standby state in the buffer, etc. By transmitting the dynamic variables required for allocation, it guarantees the performance of priority-based real-time service traffic while providing the structure to maximize the performance of effective bit rate traffic.

Description

Medium Access Control Protocol for Dynamic Resource Allocation in the Wireless ATM Networks

The initial medium access protocol of wireless ATM was designed mainly for low speed data services and could not meet the needs of various services for multimedia. In addition, most of the existing wireless ATM's medium access protocols focus on high-speed wireless transmissions, or can be extended to ATM cell scheduling algorithms from wired ATM networks to wireless ATM networks, or to support high-speed real-time traffic. It focuses on improving existing wireless media access protocols.

In the conventional wireless medium access protocol, the cell loss problem is severe and fixed at the maximum cell rate in the variable bit rate adaptation method considering the average cell rate because the average cell rate and maximum cell rate of variable bit rate traffic cannot be effectively supported. In the variable bit rate accommodating method in which bandwidth is allocated, slots that are not used have low bandwidth utilization efficiency.

In order to solve the above problems, the present invention proposes an efficient wireless ATM network-mapped access protocol capable of guaranteeing the quality of service requirements of ATM for each traffic class having various characteristics, thereby simplifying slot allocation implementation and quality of service. It is an object of the present invention to increase the efficiency of transmission using dynamic variables required for bandwidth allocation by real-time processing based on priority and considering the guarantee problem of the same time.

In order to achieve the above object, the present invention sets the minimum effective bit rate bandwidth to improve the delay and network throughput according to the slot contention scheme for access in the uplink for the effective bit rate traffic, It provides a structure that maximizes the performance of effective bit rate traffic while ensuring the performance of priority-based real-time service traffic by transmitting dynamic variables required for band allocation such as standby state in the buffer.

Operation Mechanism of Media Access Control Protocol According to the Present Invention

The proposed medium access control protocol uses time division multiple access (TDMA) as a multiple access method and has a frame structure as shown in Figure 1.

Figure 1 Frame Structure of Media Access Control Protocol

In the uplink and downlink frames, there are information slots in which packets of an ATM cell unit are transmitted. On the other hand, in the uplink, there is a request access slot (RAS) for competition and a request slot (RS-VBR) for a non-competitive variable bit rate service. It consists of a small mini-slot for scheduling and control slots (SCS).

The slot structure of the invented media access control protocol is shown in Figure 2, and among the required slots on the uplink, the access request slot is initially uplinked for all traffic classes using the slotted Aloha protocol having priority. Used in competition to connect In addition, the request slot for the variable bit rate service has a non-competitive request slot used for requesting the bandwidth required from the mobile station to the base station in order to reserve the variable bit rate traffic in units of frames.

Figure 2 Slot Structure of Media Access Control Protocol

Let us explain the operation mechanism for the medium access control protocol proposed by the present invention. The base station collects and uses information on mobile stations to determine period and slot assignments, and assigns slot assignment information, acknowledgment (ACK) signal, retransmission request, and wireless control signal to each mobile station through downlink scheduling and control slot. And so on.

When a new call of continuous bit rate arrives, the mobile station initially requests access through contention of access request slots on the uplink. If the access request is successful, the base station allocates the requested bandwidth to the information slot on the uplink, and transmits a confirmation signal through the scheduling and control slot on the downlink. After the access request, the mobile station scans the scheduling and control slots on the downlink to confirm whether the slot is allocated in the information slot as a result of the access request. If the connection request of continuous bit rate traffic is successful, the required bandwidth per frame is fixed and reserved by frame until the end of the service, so the mobile station transmits the ATM cell to the slot allocated to the information slot on the uplink.

When a new call of variable bit rate arrives, the mobile station initially requests access through contention of access request slots on the uplink. If the access request is successful, the base station allocates the requested bandwidth to the information slot on the uplink and transmits an acknowledgment signal through the scheduling and control slot on the downlink. After the access request, the mobile station scans the scheduling and control slots on the downlink to confirm the success of the access request, and then transmits an ATM cell to the information slot and sends the size of the bandwidth required for the next frame through the request slot for the variable bit rate service. Notify the base station. This non-competitive bandwidth allocation request is made every frame until the variable bit rate service is terminated through a request slot for the variable bit rate service, so that a variable bit rate ATM cell can be transmitted in real time.

When a new call of the effective bit rate arrives, the mobile terminal also requests access through contention of the access request slot on the uplink. If the access request is successful, the base station allocates the requested bandwidth to the information slot on the uplink and transmits an acknowledgment signal through the scheduling and control slot on the downlink. After the access request, the mobile station scans the scheduling and control slots on the downlink to confirm the success of the access request. If successful, the mobile station transmits an ATM cell of an effective bit rate to the allocated information slot on the uplink. In this case, the base station allocates a band for the service of the continuous bit rate and the variable bit rate, and if there is an extra bandwidth for the effective bit rate, the base station allocates the downlink scheduling and control slot according to the service class such as the buffer length or the allowable delay of the mobile station. Continue slot allocation for ABR traffic. Therefore, in the case of effective bit rate traffic that has been successfully connected once, the mobile station scans scheduling and control slots on the downlink without competing through access request slots for each frame to transmit ATM cells of the next frame. Check and transmit ATM cell if there is an assigned slot. If no slot is allocated, the bandwidth request is requested again through contention of the access request slot. This scheme can prevent a degradation in throughput due to contention of connection requests every frame of effective bit rate traffic.

In wireless ATM, it is necessary to implement statistical multiplexing to realize quality of service and requirements for various services defined in existing ATM network through media access control protocol of dynamic reservation technique. However, it is difficult to grasp the traffic situation directly from the distributed mobile terminal, and thus, it is difficult to have statistical statistical multiplexing. Therefore, there is a need for a scheduling function that can perform dynamic slot allocation according to various traffic through the central base station as shown in Figure 3.

Figure 3 Signaling Scheme for Dynamic Slot Allocation

Figure 4 shows the bandwidth allocation for each traffic in the proposed medium access control protocol. For continuous bit rate traffic, all `reservations of bandwidth according to cell transmission rate are made and the slot is fixed and allocated periodically. For real-time variable bit rate traffic, dynamic reservation allocation is performed for transmitting ATM cells in real time using a variable bit rate bandwidth requirement variable transmitted through a request slot for a variable bit rate service for each frame. The effective bit rate traffic is dynamically allocated and the media access control scheduler of the base station sets the minimum effective bit rate bandwidth to secure the minimum guarantee for connection of the effective bit rate service of the mobile station. Therefore, if the total required bandwidth for continuous bit rate and variable bit rate traffic exceeds the total remaining bandwidth except for the minimum effective bit rate bandwidth, the newly arrived continuous bit rate call is rejected and lost by call connection control, and is changed during this period. Bit rate traffic is lost due to overflow.

Figure 4 Bandwidth Allocation Scheme for Traffic

In the conventional wireless medium access protocol, the cell loss problem is severe and fixed at the maximum cell rate in the variable bit rate adaptation method considering the average cell rate because the average cell rate and maximum cell rate of variable bit rate traffic cannot be effectively supported. In the variable bit rate accommodating method in which bandwidth is allocated, slots that are not used have low bandwidth usage efficiency. However, in the present invention, the dynamic reservation for each frame can be performed in real time based on priority in consideration of the simplification of slot allocation implementation and the problem of guaranteeing the quality of service at the same time. Can increase. In addition, for effective bit rate traffic, the minimum effective bit rate bandwidth is set to improve the delay and network throughput according to the slot contention scheme for access in the uplink, and the bandwidth such as the traffic occurrence rate of the mobile station and the standby state in the buffer. Through transmission of dynamic variables required for allocation, guaranteeing performance for priority-based real-time service traffic, and providing a structure that maximizes the performance of effective bit rate traffic, throughput due to competition of access request every frame of effective bit rate traffic The fall can be prevented.

Claims (6)

Small sized minislot for configuration of access request slot for contention on the uplink and request slot for non-competitive variable bit rate service in the wireless ATM network, scheduling from the base station to the mobile terminal and control slot on the downlink How to configure (mini-slot). A slot structure having a priority of access request slot among uplink request slots for the invented medium access control protocol for wireless ATM. Slot assignment information, acknowledgment (ACK) signal, retransmission request, radio control signal to each mobile station through downlink scheduling and control slot of mobile station of base station related to operation mechanism of invented medium access protocol for wireless ATM As such. In the wireless ATM, a scheduling function capable of performing dynamic slot allocation according to various traffic through a base station in the central access control protocol of the dynamic reservation technique. In a wireless ATM network, a mobile terminal of effective bit rate traffic checks a slot allocated to itself by scanning a scheduling and control slot on a downlink without competing through an access request slot for each frame for ATM cell transmission. A function that ensures the minimum guarantee of connection of effective bit rate service of mobile station that sets minimum effective bit rate bandwidth by media access control scheduler in base station.