This paper proposes a semi-random backoff (SRB) method that enables resource reservation in contention-based wireless LANs. The proposed SRB is fundamentally different from traditional random backoff methods because it provides an easy migration path from random backoffs to deterministic slot assignments. The central idea of the SRB is for the wireless station to set its backoff counter to a deterministic value upon a successful packet transmission. This deterministic value will allow the station to reuse the time-slot in consecutive backoff cycles. When multiple stations with successful packet transmissions reuse their respective time-slots, the collision probability is reduced, and the channel achieves the equivalence of resource reservation. In case of a failed packet transmission, a station will revert to the standard random backoff method and probe for a new available time-slot. The proposed SRB method can be readily applied to both 802.11 DCF and 802.11e EDCA networks with minimum modification to the existing DCF/EDCA implementations. Theoretical analysis and simulation results validate the superior performance of the SRB for small-scale and heavily loaded wireless LANs. When combined with an adaptive mechanism and a persistent backoff process, SRB can also be effective for large-scale and lightly loaded wireless networks.

802.11e HCCA (Hybrid coordination function Controlled Channel Access) exhibits good QoS provisioning for constant bit rate (CBR) video streams in a single collision domain. However, its performance degrades significantly for variable bit rate (VBR) video streams particularly in multi-collision domains. In addition, HCCA has the disadvantage of high complexity. In this paper, we introduce a deterministic backoff (DEB) method into the HCCA mechanism, which achieves virtual polling via carrier sense on the wireless channel. DEB inherits the merit of HCCA that achieves near collision-free channel access in single collision domain. It also exhibits robust performance in multi-collision domains. Simulation results show that DEB supports well both CBR and VBR video streams.

QoS provisioning for video streaming over 802.11 home networks is challenging due to the tight bandwidth and delay constraints. Currently, both 802.11e HCCA and EDCA have their disadvantages when delivering video over 802.11 networks. EDCA exhibits degraded QoS performance for increased number of stations, while HCCA has high complexity, and also suffers from the impact of inter-cell interference. In this paper, we propose a new backoff mechanism which is fundamentally different from traditional random backoff methods in 802.11. The mechanism achieves resource reservation by reusing one or multiple time slots for transmission in consecutive backoff cycles. The basic idea is borrowed from R-ALOHA, but several modifications are made to allow it to work in the context of CSMA network. An additive increase multiplicative decrease based algorithm is proposed to control resource allocation for video streaming in the 802.11 network. Theoretical analysis and numerical simulations are conducted to validate the effectiveness of the method and the algorithm.

In this paper, we propose a semi-random backoff (SRB) mechanism to combat network collisions for 802.11 DCF/EDCA in wireless LANs. SRB is fundamentally different from traditional random backoff methods because it provides a form of resource reservation at no extra cost. The key idea of SRB is to set the backoff counter to a deterministic value upon a successful transmission. This allows a station to reuse a time slot in consecutive backoff cycles without colliding with other stations, thus achieving resource reservations. In cases of failed transmissions due to network collisions or channel errors, SRB automatically reverts to the standard random backoff method. SRB can be readily applied to both 802.11 DCF and 802.11e EDCA networks with minimum modification to the existing DCF/EDCA implementations. Theoretical analysis and simulations are conducted to evaluate this new method and our results validate its good performance in small to middle-sized 802.11 wireless LANs.