This paper evaluates the performances of the contention-based channel access mechanism of IEEE 802.11e, called enhanced distributed coordination function (EDCF), compared with the 802.11 legacy MAC in supporting voice, video and data applications through network simulation of a scenario of 802.11e. Then we discuss the effects of Contention Window (CW) and Arbitration Inter-Frame Space (AIFS) on service differentiation and total throughput. We also consider an optional feature of the EDCF, called contention-free burst (CFB). Through our simulation study, we can draw a conclusion that the EDCF with TXOP can provide better-differentiated channel access for different traffic types than EDCF without TXOP especially at high traffic load conditions. But the movements caused by the parameters in CFB seem a lot bouncing and instability when in different application and configuration.
This research mainly focuses on the performance evaluation and the improvement of the IEEE 802.11 DCF. The basic access method in the IEEE 802.11 MAC protocol is the distributed coordination function (DCF), which is a carrier sense multiple access with collision avoidance (CSMA/CA) MAC protocol. In this paper, we first evaluate the performance of DCF using the classical Markov analytical model proposed by Bianchi, and then present an improvement named TDCF. Both the theoretical computation and the simulation in our research prove that TDCF has better performance than DCF.
In this paper, two wireless broadband access and accounting schemes were introduced. There are some differences in the client and the access router module between them. In one scheme, Secure Shell (SSH) protocol is used in the access system. The SSH server makes the authentication based on private key cryptography. The advantage of this scheme is the security of the user's information, and we have sophisticated access control. In the other scheme, Secure Sockets Layer (SSL) protocol is used the access system. It uses the technology of public privacy key. Nowadays, web browser generally combines HTTP and SSL protocol and we use the SSL protocol to implement the encryption of the data between the clients and the access route. The schemes are same in the radius sever part. Remote Authentication Dial in User Service (RADIUS), as a security protocol in the form of Client/Sever, is becoming an authentication/accounting protocol for standard access to the Internet. It will be explained in a flow chart. In our scheme, the access router serves as the client to the radius server.
IEEE 802.11 WLAN is used widely because of the flexibility of Wireless LAN. Subscribers hope that the Wireless LAN can supply Real-time application as the wired network, for example, video and voice service, these require service differentiation in networks. Service differentiation at the IP layer is useless without support of that in lower layers. This support is even more critical in wireless networks because of its instability and limited bandwidth. This paper aims at the promotion of data stream transfer through research in TCP/UDP transfer over MAC layer supported by EDCF. Applications impose requirements on communication parameters, such as data rate and delay. In this paper we present ideas to provide service differentiation support for 802.11e and compare it with the legacy DCF of IEEE802.11 by simulation, and analyze the result in performance of the schemes with TCP and UDP flows.