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A multihop relay extension for IEEE 802.16e systems is the subject of ongoing standardization activities within the IEEE 802.16j Task Group. The emerging IEEE 802.16J standard enhances the 802.16e PHY and MAC to enable support of multihop routes between a mobile station and a base station through intermediate relay stations. Since it is believed that the capacity of a single-hop 802.16e system is...
Different types of power-saving techniques have been proposed in various fields to alleviate the limitation on the battery lifetime for the mobile stations (MSs). In order to provide feasible energy-conserving mechanism, three different power-saving types have been introduced in the IEEE 802.16e broadband wireless networks. By means of pre-negotiations, the MS can be absent from the serving base station...
Relay stations (RSs) are usually used to enhance the signal strength for the users close to the cell boundary. However, transmission through a relay station needs two transmission phases, i.e., one is from the base station to the relay station and the other is from relay station to mobile stations. Thus, relay may also decrease system capacity if two-phase transmission time is considered. As a result,...
Physical Carrier Sensing plays a crucial role in the effectiveness of CSMA-based MAC protocols, yet its properties and impact on the system performance under slow fading channel have not been well understood. We demonstrate that carrier sensing can be highly unreliable even within the "carrier sensing range" and the channel is largely stable during a transmission between slowly moving mobile...
Due to the small radio area covered by an Access Point (AP), handoffs frequently occur in Wireless Local Area Networks (WLANs) as Mobile Stations (MSs) move their associations from one AP to another. This paper presents a new handoff management scheme to support ongoing real-time applications while MSs change their network point of attachment. This approach consists of minimizing the total number...
Today's IEEE 802.11 Wireless LANs (WLANs) usually support multiple transmission rates, where mobile stations adapt their data rates based on their link adaptation strategies. In this paper we analyze the throughput performance of multi-rate WLANs with link adaptation. Specifically, an analytical model is developed to derive the system throughput of both the basic access and RTS/CTS mechanisms. The...
In this paper the autocorrelation properties of shadow fading and angle spread at both the base station (BS) and at the mobile station (MS) are analyzed using urban macro cellular measurement data. The shadow fading parameter is shown to have a longer decorrelation distance than the angle spread at both the BS and at the MS. Furthermore, we observe variations in the shadow fading that depend on the...
We establish a closed form formula of the other-cell interference factor f for omni-directional and sectored cellular networks, as a function of the location of the mobile. That formula is based on a fluid model of cellular networks: The key idea is to consider the discrete base stations (BS) entities as a continuum of transmitters which are spatially distributed in the network. Simulations show that...
The mobile WiMAX systems based on IEEE 802.16e-2005 provide high data rate for the mobile wireless network. However, the link quality is frequently unstable owing to the long-distance and air interference and therefore impacts real-time applications. Thus, a bandwidth allocation algorithm is required to be modulation-aware, while further satisfying the latency guarantee, service differentiation and...
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