The combination of VoIP and WiMAX should overcome the bottleneck of technology

Both VoIP and WiMAX pose a threat and challenge to traditional technologies in their respective areas. The combination of them will also make new demands and new effects on the development of communication technology.

Priority support for VoIP services

For WiMAX, VoIP voice service as a basic business type must be supported first.

WiMAX network based on IP protocol, mainly provide broadband data services, but only to provide traditional web browsing, such as broadband data services can not meet the requirements of operators and market expansion, therefore, the WiMAX Forum application Team (AWG) proposed a variety of new different QoS requirements of the business, Where VoIP is a priority-supported business type. To sum up, we can see that the development of VoIP business from the fixed system to the mobile system, WiMAX system from the data services to the Voice business evolution, both promote development, the combination of the point is the VoIP application of WiMAX system.

VoIP Service requirements system can provide to ensure bandwidth, delay and delay jitter control in a certain range, no QoS support system can not meet the above requirements. Therefore, the difficulty of the WiMAX system VoIP service lies in the End-to-end QoS support capability of the whole VoIP session, including the licensing of VoIP traffic, the conversation negotiation and the wireless resource allocation and scheduling after the session is established, especially in the mobile environment, When a user moves from one base station to another, the packet loss and delay must be controlled in a strict range, and the QoS can remain unchanged after switching. The End-to-end QoS solution consists of two aspects: the QoS capability of the air interface and the network side QoS architecture. (Computer science)

End to end QoS solution

WiMAX air Interface QoS mechanism is implemented at MAC layer. The QoS mechanism consists of two parts, part on the management of the business flow, which provides a mechanism for implementing QoS management on the top and bottom lines. The other part is the corresponding QoS guarantee mechanism, including scheduling algorithm, buffer pool management and flow control, in the protocol of these algorithms are not defined and elaborated, by the specific implementation of the equipment manufacturers decision. Business Flow Management consists of the following:

* For connection-oriented services, the MAC layer is for each connection.

* Five QoS service types for air interface and related parameters, these five types are: non-requested Bandwidth allocation Service (UGS), real-time polling service (RTPS), extended real-time polling service (Extended real-time Polling Service,ertps), Non-real-time polling business (NRTPS) and best Practices (BE).

* Define QoS parameters for each user, including metrics such as rate, latency, and so on.

* Policy conditions that allow new business flows to be established.

The QoS implementation mechanism of air interface is closely related to classifier, first, the IP packets sent by the upper layer are associated with a business flow identified by the connection identifier (CID), and the MAC packets are formed, and the QoS service types and corresponding parameters of the packets are included in the CID. Makes each packet have the corresponding QoS requirements before scheduling. The QoS support of the IEEE802.16MAC protocol is divided into 3 parts: first create the initial business flow and configure the QoS parameters of the traffic flow, and then dynamically manage the business flow, including dynamic business Increase (DSA), dynamic Service Change (DSC) and Dynamic service deletion (DSD); At last, the Packet Data Unit (PDU) of Mac is classified in the communication process, and the priority is sorted according to the category of business flow.

On the network side, WiMAX forum NWG's Network Architecture specification defines the QoS logic entities, triggering processes, and corresponding messages in the network for 5 QoS types that support empty, by configuring the QoS control unit in BS and ASN, The QoS architecture is extended based on the IEEE802.16 standard. The WiMAX network QoS feature model includes the following QoS function units:

*qos the policy database. The ownership of the SS NSP maintains a pre-defined policy database for authentication and authorization of WiMAX business requests.

* Apply function AF. The ownership of the SS NSP supports the application function. SS can interact with AF using the Application Layer Control protocol, and as a response, AF can emit WiMAX's business flow excitation to PF.

*SFM. The Business Flow Management (SFM) logical entity is located within the ASN, which is responsible for creating, licensing, activating, modifying, and deleting business streams. It consists of the admission Control (AC) feature and the associated local resource information.

*SFA. The Business Flow Authorization (SFA) logical entity is located within the ASN, which is responsible for network-level license control based on resource management policies. SFA consists of a QoS policy database and related policy functional blocks (PF). The policy database loads user-predefined QoS attribute information from the user's vesting NSP in the AAA process.

The QoS policy database is located within the ASN. With the AAA process, QoS-related information in user properties can be transferred from a predefined database belonging to NSP to the ASN. Cross-zone QoS information acquisition can only be done through the R3 interface or the R5 interface, and must be consistent with the original QoS attribute.

The QoS attribute of the user can be considered only for the MAC connection of the air interface, that is to say, the QoS attribute does not specify the QoS implementation method of the specific access network and the core network.

The QoS implementation method of access network and core network is related to the mechanism of QoS implementation in fixed networks.

There are still technical bottlenecks

We can see that WiMAX network in order to support QoS requirements such as VoIP business, from the empty to the network side has established a relatively perfect QoS mechanism and architecture, but in some technical issues are not clear, for example, VoIP services in the ASN, the ASN move under the QoS guarantee Mechanism, The perfection and reliability of network structure, security and authentication, etc., these problems are not only limited to WiMAX system, for any wireless system based on IP protocol have the same problem, so the research of WiMAX technology is of great significance to the application of VoIP service in mobile communication system. We look forward to the resolution and breakthrough of these problems.

The combination of VoIP and WiMAX is a good way to achieve the advantages of complementarity, and also fit well with the development of communication technology trends. On the other hand, the combination of the two is still facing some technical bottlenecks which can not be overcome in the short term, such as: the QoS guarantee mechanism in mobile environment, the perfection and reliability of network structure, security and authentication, etc. From this point of view, the future of technological development will certainly experience a certain difficult process.