Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-08-03
2003-09-16
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S338000, C370S348000, C370S397000, C455S445000
Reexamination Certificate
active
06621805
ABSTRACT:
TECHNICAL FIELD
The present invention is related to network communications. More particularly, this specification discloses a method and an apparatus for the generation and maintenance of a wireless ad-hoc network for multicasting real-time variable-bit-rate (VBR) data among a plurality of nodes.
BACKGROUND
Wireless ad-hoc networks consist of collections of “peer” mobile nodes, capable of communicating with each other, and forming a dynamically changing network with no infrastructure. In order to route packets to a destination node, each node in a wireless ad-hoc network uses other nodes in the network as relays. Therefore, it is desirable that the nodes in the network establish routing among themselves, and that the routes keep changing as the nodes move, or as the environment changes due to such factors as fading and interference. Many routing protocols have been proposed to enable effective routing in such an environment, examples of which are provided in the articles cited below. In particular, multicasting has received much attention in the Internet community. Most of the development in multicast protocols, however, has addressed wireline, fixed networks having static topologies, and are focused toward Internet applications. The majority of these Internet multicast protocols do not consider the issue of resource reservation, because the available bandwidth is generally not a problem in wireline networks. Recently, the Core-Assisted Mesh Protocol (CAMP) was proposed for effective wireless multicasting of datagram traffic. However, CAMP neither supports real-time traffic nor does it attempt to guarantee any level of quality of service (QoS). No protocol developed to date addresses multicast streaming of real-time data in a wireless ad-hoc network environment.
Most multicast protocols result in the formation of a multicast structure, which is used for transportation of multicast data. Some schemes utilize core nodes or rendezvous points, which are used to collect multicast data from sources (if there are more than one) and then to multicast the data from these nodes to the receivers. The structure built typically takes the form of a tree or a mesh.
QoS is currently a focal point of attention in both wireline and wireless networks. There are two major ideologies for delivering QoS guarantees: the integrated services model and the differentiated services model. The integrated services model attempts to provide a guaranteed notion of service, which involves reserving bandwidth from the source node to the destination node. RSVP is a signaling protocol which supports reservation of resources for multicast sessions in the Internet and is part of the integrated services specification. On the other hand, the differentiated services model is based on assigning resources to a user or edge router on a quasi-static basis. The resource is thus reserved based on what is called a service level agreement (SLA) and is then used to carry multiple classes of data. Each class of data receives a particular quality of service in terms of per-hop forwarding at each router. While, the differentiated services model is much simpler to implement than the integrated services model, it does not provide strict end-to-end quality of service guarantees in terms of bandwidth or delay.
Presently, there is a need for a multicasting method and system that is capable of supporting real-time variable bit-rate (VBR) data among the nodes of a wireless network. It is also desirable that the system be distributed, highly adaptive to variations, flexible, and scalable. Several heuristic methods have appeared in the literature, and are cited below, with the goal of developing collision-free transmission schedules. Furthermore, other approaches, also cited below, have been developed which relax the strict collision-free requirement, and in which nodes are allowed to transmit the same packet several times, where the method guarantees that at least one transmission is collision-free. Although this approach makes scheduling transparent to the network topology changes, it has the disadvantage that a packet might encounter many collisions before being able to transmit collision-free, thus significantly impacting network throughput.
A related multicast scheduler has been presented in application titled “Method and Apparatus for Multicasting Real-Time Traffic in Wireless-Ad-Hoc Networks” for the provision of multicasting real-time constant bit-rate (CBR) traffic in a wireless ad-hoc network. However, real-time bursty VBR traffic presents a more difficult challenge for performing resource allocation because of its dynamically changing bandwidth requirements and its sensitivity to delay jitter. VBR traffic is both delay-sensitive and has a high degree of burstiness. For example, the peak bit-rate of video sources is several times that of their average bit rate. If bandwidth is allocated to satisfy the peak rate, the result is extremely inefficient bandwidth utilization. This kind of allocation can be sufficient for wired Internet applications, where bandwidth abounds, but the scarcity of wireless bandwidth makes this approach unacceptable for wireless ad-hoc networks. Thus, it is desirable to provide a means to reserve bandwidth adaptively in order to match the burst rate of the source dynamically. It is further desirable to re-use unused bandwidth for other applications.
References
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SUMMARY
The present invention provides a method and an apparatus for transmission of variable bit-rate data through a wireless network. Specifically, the method of the present invention provides for bandwidth reservation for real-time traffic in a wireless ad-hoc network having a plurality of nodes transmitting and receiving data via a plurality of colors, with the transmitting and receiving of the data being performed periodically with a data period
2
. Each of the plurality of nodes has a either a con
Dao Son
Kondylis George D.
Krishnamurthy Srikanth V.
HRL Laboratories LLC
Hsu Alpus H.
Qureshi Afsar M.
Tope-McKay & Associates
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