K Ban

Multihop sensor network design for wide-band communications

This paper presents a master/slave cellular-based mobile ad hoc network architecture for multihop multimedia communications. The proposed network is based on a new paradigm for solving the problem of cluster-based ad hoc routing when utilizing existing wireless local area network (WLAN) technologies. The network architecture is a mixture of two different types of networks: infrastructure (master-and-slave) and ad hoc. In this architecture, the participating slave nodes (SNs) in each cluster communicate with each other via their respective master nodes (MNs) in an infrastructure network. In contrast to traditional cellular networks where the base stations are fixed (e.g., interconnected via a wired backbone), in this network the MNs (e.g., base stations) are mobile; thus, interconnection is accomplished dynamically and in an ad hoc manner. For network implementation, the IEEE 802.11 WLAN has been deployed. Since there is no stationary node in this network, all the nodes in a cluster may have to move together as a group. However, in order to allow a mobile node to move to another cluster, which requires changing its point of attachment, a handoff process utilizing Mobile IP version 6 (IPv6) has been considered. For ad hoc routing between the master nodes (i.e., MNs), the Ad hoc On-demand Distance Vector (AODV) Routing protocol has been deployed. In assessing the network performance, field test trials have been carried out to measure the proposed network performance. These measurements include packet loss, delays under various test conditions such as a change of ad hoc route, handoffs, etc.

Dynamic adjustment packet control for video communications over ad-hoc networks

This paper is concerned with transporting video information via multihop mobile ad-hoc channels. The major problem with transmitting real-time video information over these channels is the issue of link reliability. To improve the quality of the video reception we propose a cross layer feedback control mechanism that can allow the application layer to adapt itself to a dynamically changing network topology. We also present packet transmission strategies capable of recovering video signals under long bursts of packet drops, typical of a route change condition. This feedback control scheme has been developed for transmission of RTP/UDP/IP packets using the emerging H.264/AVC video-coding standard.

Video transmission for multi-hop networks using IEEE 802.11 FHSS

In many applications, such as construction, manufacturing, ground robotic vehicles, and rescue operations, there are many issues that necessitate the capability of transmitting digital video and that such transmissions should be performed wirelessly and in an ad-hoc manner. Recently, we proposed an ad-hoc, cluster-based, multi-hop network architecture for video communications (see Gharavi, H. and Ban, K., 3G Wireless Conference, 2002). For implementation, the IEEE 802.11 FHSS wireless LAN system using 2GFSK modulation was employed. To enhance the overall throughput rate for higher quality video communications, we present a performance evaluation of the IEEE 802.11 FHSS when 4GFSK modulation option is selected. Unfortunately, the 2 Mb/s system utilizing 4GFSK modulation is not very efficient in terms of RF range. Therefore, to improve its performance for multi-hop applications, a combination of diversity and non-coherent Viterbi based receiver is considered. For the video transmission part, we have considered a bitstream. splitting technique together with a packet-based error protection strategy to combat packet drops under multipath fading conditions. Finally, the paper presents simulation results, including the effects of receiver design and diversity on the quality of the received video signals.

RTCP-based frame-synchronized feedback control for IP-video communications over multipath fading channels

This paper presents a packet-loss feedback tracking scheme for the transmission of video signals over mobile channels. The proposed feedback scheme is based on the real time transport control protocol (RTCP), which is designed to provide an end-to-end feedback assessment of transmitted packets on a frame-by-frame basis (video frame). In addition, the frame synchronized RTCP-based feedback scheme is designed to take care of losses of RTCP packets due to bad channels. The video encoder, upon receiving its feedback report, can identify the exact location of the missing packets in the transmitted video frame. The feedback scheme is then applied to transport H.264/RTP/UDP/IP packets in real-time. A packet-loss compensation strategy has been used to assess the quality of the received signal under multipath fading channel conditions.

IEEE 802.11 FHSS receiver design for cluster-based multihop video communications†

Recently, we proposed an ad hoc, cluster-based, multihop network architecture for video communications using IEEE 802.11 FHSS (Frequency Hopping Spread Spectrum) wireless LAN (WLAN) technology with 2GFSK (2-level Gaussian Frequency Shift Keying) modulation capable of 1 Mb s−1 transmission. To increase the transmission rate to 2 Mb s−1 for higher-quality video communications, we evaluated the performance of the IEEE 802.11 FHSS system when a 4GFSK modulation option is selected. Since the 2 Mb s−1 system utilizing 4GFSK modulation is not very efficient in terms of Radio Frequency (RF) range, to improve its performance for multihop applications a combination of diversity and noncoherent Viterbi equalizer are considered. For video transmission, we employed a bitstream-splitting technique together with a packet-based error-protection strategy to combat packet drops under multipath fading conditions. The real-time transport protocol (RTP), user datagram protocol (UDP), and Internet protocol (IP) are used for video streaming. This includes an RTP packetization scheme to control the packet size and to improve the error-resilient decoding of the partitioned video signal. The paper includes the simulation results showing the effects of the receiver design and diversity on the quality of the received video signals. Copyright

A Link-Level Simulator of the cdma2000 Reverse-Link Physical Layer

The cdma2000 system is an evolutionary enhancement of the IS-95 standards which support 3G services defined by the International Telecommunications Union (ITU). cdma2000 comes in two phases: 1XRTT and 3XRTT (1X and 3X indicates the number of 1.25 MHz wide radio carrier channels used and RTT stands for Radio Transmission Technology). The cdma2000 1XRTT, which operates within a 1.25 MHz bandwidth, can be utilized in existing IS-95 CDMA channels as it uses the same bandwidth, while 3XRTT requires the commitment of 5 MHz bandwidth to support higher data rates. This paper describes a software model implementation of the cdma2000 reverse link and its application for evaluating the effect of rake receiver design parameters on the system performance under various multipath fading conditions. The cdma2000 models were developed at the National Institute of Standards and Technology (NIST), using SPW (Signal Processing Worksystem) commercial software tools. The model has been developed in a generic manner that includes all the reverse link six radio configurations and their corresponding data rates, according to cdma2000 specifications. After briefly reviewing the traffic channel characteristics of the cdma2000 reverse link (subscriber to base station), the paper discusses the rake receiver implementation including an ideal rake receiver. It then evaluates the performance of each receiver for a Spreading Rate 3 (3XRTT) operation, which is considered as a true “3G” cdma2000 technology. These evaluations are based on the vehicular IMT-2000 (International Mobile Telecommunication 2000) channel model using the link budget defined in cdma2000 specifications for the reverse link.

Group-based ad-hoc network for multimedia communications

This paper is concerned with evaluating ad-hoc networks for group-oriented tactical operations. For such operations, a cellular-based ad-hoc network architecture has been constructed for real-time multimedia communications. To assess the suitability of this network, its performance has been compared with conventional peer-to-peer ad-hoc network architectures under various test scenarios using IEEE 802.11 WLAN technology. We have shown that the cellular network, which operates in two modes: infrastructure for intracell and ad-hoc for intercell communications, is more suitable for group-based tactical missions