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The wideband channel measurements at 580 MHz, 2.35 GHz and 4.90 GHz have been performed in the urban micro- and macrocell scenarios in the cities of China with multiple-input multiple-output (MIMO) channel sounder. The measured cases include line-of-sight (LOS) and non-line-of-sight (NLOS) propagation. Statistical results and comparative analysis for both scenarios are presented in this paper, including...
The problem of tandem vocoders and their effect on voice quality is well-known. In the case of international mobile-to-mobile calls, there can be up to three vocoding stages - between each mobile and its base station controller, as well as a digital circuit multiplication equipment (DCME) or voice over IP (VoIP) stages on the international link. The ITU standards for 2G and 3G networks define the...
Recently, there have been a lot of researches on hybrid duplexing (HD) to exploit advantages of both time division duplexing (TDD) and frequency division duplexing (FDD). In the next generation communication, heterogeneous cell structure in which each cell would apply proper duplexing mode independently will be raised instead of homogeneous cell structure. However, in heterogeneous cell environment,...
In next-generation cellular systems including 3.9G and IMT-advanced systems, voice-over-IP (VoIP) services will be provided to users instead of conventional circuit switch-based voice calls. VoIP packets have peculiar characteristics that the packet length is short and packets are frequently generated. These phenomena require significant radio resources to send control channels in which resource assignment...
We review previous resource allocation algorithms for voice over IP (VoIP) services in Mobile WiMAX based on the IEEE 802.16e-2005 standard, and propose a new algorithm that allocates radio resources in the consideration of packet-size and packet-generation period variations of wireless VoIP codecs; hence, we can improve the efficiency of resource utilization in Mobile WiMAX. Through simulations,...
The Network Mobility Basic Support (NEMO BS) protocol is the IETF standard to manage the mobility of entire IPv6 networks. One of the typical applications of this protocol is to deploy NEMO BS in transportations such as train or bus. As a result, passengers can benefit from global and permanent IPv6 connectivity with legacy IPv6 terminals equipped with a common wireless technology such as Wi-Fi. However,...
This paper presents CDMAN1 (collaborative data management in ad hoc network) a data sharing system designed for mobile ad hoc networks (MANETs). This system targets limited capability devices such as PDAs. In particular it takes into account limited battery capacity and limited memory. CDMAN is based on structured segmented data. This paper analyzes how structured segmented data improve the system...
Seamless vertical handover is one of the major challenges toward seamless inter-networking between heterogeneous access networks. To perform seamless vertical handover even under bad radio conditions in network mobility (NEMO) environments, NEMO-SHO has been proposed as an IPv6 soft handover extension that allows packet bicasting via two different wireless links simultaneously. However, the performance...
In this paper, we propose and analyse a new scheme to handle ranging requests in IEEE 802.16e networks based on differentiated backoff parameters and a novel hierarchical code partitioning principle. Our analysis is of the form of a fixed-point equation which characterizes the system operating points and which allows us to compute the attempt rate of each QoS class as well as the distribution of the...
Mobile devices that are equipped with multiple interfaces should choose the best path for each application. In this paper, we propose a new algorithm for path selection on multihomed end-hosts. The algorithm operates in two steps. The first step consists of using a MADM algorithm to allocate score to paths. These scores are then used by a bi-objective tasks assignment function which proposes a global...
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