Persistent communication with changing environment

Details Persistent communication with changing environment Persistent communication with changing environment

1999-12-06

2003-11-11

Ngo, Ricky (Department: 2697)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S338000, C370S401000, C370S352000, C370S475000, C455S436000

Reexamination Certificate

active

06647001

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to address routed communication, such as packet switched sessions, carrying continuous types of media and more particularly to continuing or maintaining the communication through address changes.
2. Background Information
In communication systems, there are two general types of communication routing. One type uses what is generally referred to as a circuit switched routing system. The other type uses what is generally referred to a packet switched, or address routed system.
In a circuit switched system, a communication session is established between two or more terminals and the required communication resources (bandwidth, channels, etc.) are assigned to the session until the session ends, or otherwise changes. The public switched telephone network (PSTN) is generally considered a circuit switched system. A call is assigned communication resources when the caller places the call and those resources are indefinitely assigned to that call. In a circuit switched system carrying voice communications, signal latency is typically a primary design consideration, while signal loss or distortion is a secondary design consideration. In simple terms, fast is better than perfect. This is appropriate for voice communication, where a person adjusts to distortion or loss in quality much easier than they adjust to delay.
With the advent of data networks and the need to transport data between and across those networks, a different type of communication system has evolved. These data networks typically establish a communication session using a communication stream that is divided into individually addressed data bursts or packets. These information packets have address information appended to the data and are routed across the communication medium using that address information. However, in contrast to a circuit switched network, the connections for this type of communication are established by a switching matrix that routes the data packets based on the appended address information. As the switching matrix and loading changes dynamically, individual data packets are frequently routed through different paths from the source to the destination, arriving out of order. To compensate for the change in order, some form of data buffering is required at the receiver, which can introduce delay. In addition, error correction may require that data packets be re-transmitted if the receiving terminal detects an error. Buffering and error correction both introduce delay. In a packet switched communication system, a primary consideration is maintaining data integrity and eliminating errors, while a secondary consideration is data latency. In simple terms, information integrity and fidelity is better than speed of delivery for most data. This is of course appropriate for data, where the data may have no value if it includes a single error.
There are a number of known data networking protocols, which include: TCP/IP; UDP/IP; NetBEUI; & IPX/SPX. Most of these data networking protocols are appropriate for packet switched or address routed communication, though they may have been developed for specialized applications or equipment.
Different transport media are integrated and part of the circuit switched and packet switched communication transmission systems. Some transmission systems use wired transport media and others use wireless. Wired or terrestrial transmission systems include twisted pair, coaxial, and fiber optic. Other assorted transmission systems, which are used in conjunction with wireless systems include light frequency, and radio frequency systems. Some of these transport media are more commonly associated with circuit switched systems and other transport media are more commonly associated with packet switched systems. However, the inter-connection and cross-over of the different types of systems is on-going.
In addition, there are hybrid protocols and services, such as Asynchronous Transfer Mode (ATM). From the user perspective, ATM service can provide what appears to be a virtual circuit switched session using packet switched protocols. This is because the user can request and get a quality of service guarantee (the users request or reserve a specified signal latency, with specified error tolerance).
Many of these different protocols and media have been adapted to handle large bandwidth real-time applications from fixed point to fixed point. As a result, a user at a desktop computer can connect using a wired or wireless connection to a streaming multi-media server over the Internet using packet switching techniques and protocols and participate in a streaming multi-media session that displays characteristics of a circuit switched network.
With the appropriate conditions, the user is able to establish a streaming multi-media session with a low signal latency to provide good real-time interaction, and a low data error rate to provide good fault tolerance and error recovery. The user establishes the desired service during setup of the streaming multi-media session. The system then provides the requested service until the user terminates the session, or the user requests a change. However, if the streaming multi-media session is improperly terminated for any number of reasons, the user is unable to resume the streaming multi-media session at the exact point where they left off. As typically occurs in a streaming content session, the user must re-establish the session with the associated set-up and then replay the session up to the point of the termination or attempt to fast-forward to the point where the session was dropped or lost. If the streaming multi-media session is a live session, this may be impossible.
There are many reasons for the session to be improperly lost, dropped or terminated. One common reason for improper termination is movement of a mobile user from one cell to another cell in a cellular system. This is because cellular protocols do not adequately support streaming multi-media sessions that use address routed communications. Part of the problem is that there is little communication between the different communication layers. Changes in the transport or other lower layers can affect higher protocol or data layers. However, the techniques to exchange information between the layers are poor or non-existent.
In a streaming multi-media session, the data packets are most commonly transmitted over a packet switched network. This means that the packets and transmission system consistently rely on the source and destination addresses to properly route or switch the packets from the source to the destination. When a streaming multi-media session is established, the streaming server and the receiving or destination client exchange address information. This address information is then used during the streaming multi-media session as part of the address routing to send information packets between the server and the client. In a simplification, data packets from the server (the streaming source) include the client (destination) address in the data packet header. Data packets from the client (the stream receiver) include the server (streaming source) address in the data packet header. In this manner, the client and server are able to communicate with each other and maintain a duplex communication circuit. However, once the streaming multi-media session is established, the client and server do not expect the address information to change. Because the server does not expect the client address to change, when the address information does change in mid-session, the streaming multimedia session improperly terminates.
In a cellular system, as a mobile unit moves between cells, the supporting wireless communication circuits constantly set up and tear down the circuits between the base stations and the mobile unit. This occurs through a combination of information exchange between the mobile unit and the base stations over control channels, with set up and tear down of the communication channels for each cell. To the mobile voi

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