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This paper presents an analytical model for network throughput of WLANs, taking into account heterogeneous conditions, namely network nodes transmit different length frames with various offered load individually. The airtime concept, which is often used in multihop network analyses, is firstly applied for WLAN analysis. The proposed analytical model can cover the situation that there are saturation and nonsaturation nodes in the same network simultaneously, which is the first success in the WLAN analyses. This paper shows the network throughput characteristics of four scenarios. Scenario 1 considers the saturation throughputs for the case that one or two length frames are transmitted at the identical offered load. Scenarios 2 and 3 are prepared for investigating the cases that all network nodes transmit different length frames at the identical offered load and identical length frames at the different offered loads, respectively. The heterogeneous conditions for not only frame length but also offered load are investigated in Scenario 4.

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In IEEE 802.11 wireless multi-hop networks, each node works individually and their individual operations generate entire network dynamics. It is important to clarify the network dynamics in wireless multi-hop networks for designing and constructing multi-hop communication networks. This paper presents the network-dynamics investigations for three-hop string-topology wireless network in detail. From the investigations, a "backoff-stage synchronization" phenomenon, which is mutuality between hidden nodes, is found. The mechanism of the backoff-stage synchronization is expressed and the sufficient conditions for the synchronization occurrence are given. This phenomenon gives some impacts on the IEEE 802.11 multi-hop-network communications.

This paper proposes analytical expressions of end-to-end throughput for IEEE 802.11e Enhanced Distributed Channel Access (EDCA) wireless string-topology multi-hop networks. For obtaining the IEEE 802.11e EDCA performance, internal collisions between Access Categories (ACs) in a node, frame collisions with external nodes, and frame-existence probabilities of buffers at each AC are expressed as functions of EDCA access parameters. Therefore, it is possible to obtain the effects of the EDCA access parameters to Quality of Service (QoS) support in the EDCA. It is possible to obtain the end-to-end throughput at any offered load with respect to each AC because the buffer states can be expressed according to ACs. The obtained analytical expressions are verified by showing the quantitative agreements with simulation results.

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