Investigation On Access Control Schemes Based On QoS In IEEE 802.16

With the development of wireless communication, the contents of multimedia applications are expected to be enriched. As a competitive technology of the next-generation wireless network, IEEE 802.16 has focused on many kinds of services with QoS supported.IEEE 802.16 standard specifies QoS signaling mechanisms such as bandwidth request/allocation and service types. However, the standard leaves some important issues such as call admission control, QoS parameter mapping, traffic conditioning and packet scheduling, undefined. These problems are expected to be resolved by the developers.Admission control is very important for QoS guarantee. Its main task is to determine whether a new service can be allowed. BS (Base Station) is responsible for whether accepting or rejecting these access requests based on bandwidth long period requirement and current network states. Bandwidth resource will be assigned after service request being allowed by network. This bandwidth resource assignment maybe decrease current online services' QoS. But on the other hand, network must allow most service requests' accessed. Then these two scenarios meet a conflict. Admission control is the right method to resolve this conflict. It can remain current online service's QoS while accepting new service requests and can also guarantee most of service requests being admitted. Since IEEE 802.16 should support four kinds of scheduling services with different scheduling service QoS to guarantee more users' network access and guarantee high quality service be supported while meet QoS of different services.In general mobile network, idle radio resource will be checked before a service request is admitted. If there is enough bandwidth resource to be assigned, this service request can be allowed. This mechanism can also be introduced in IEEE 802.16 admission control algorithms. This thesis proposes two kinds of multiple services admission control algorithms for IEEE 802.16 based on other general mobile network admission control mechanism. These algorithms use service class being defined in IEEE 802.16 as their scheduling references.The first algorithm uses threshold mechanism to control admission of different priority service request. The kind of service which would be admitted is decided through the threshold of bandwidth usage. Threshold mechanism can efficiently guarantee higher priority service requests get more admission chance. But meanwhile it sacrifices lower priority service request's admission chance.The second algorithm divides the whole bandwidth resource into two parts. The first part is assigned based on service request priority and the second part is assigned based on FIFO mechanism of service requests. On the other hand, if bandwidth is in high usage status, higher prority service request can only occupy bandwidth resource which is using by lower priority in the first part. The lower priority service can be queued for next round of admission. It not only can guarantee higher priority service requests get more chance admission, but also can guarantee more users access network with high quality of service assigned. Meanwhile they decrease call blocking rate for multiple QoS service requests on the other hand.At the end of this thesis, the capability of these algorithms is verified by lab simulation. Advanced QoS support for multiple service requests is also verified.