Scheme for managing overlapping wireless computer networks

Details Scheme for managing overlapping wireless computer networks Scheme for managing overlapping wireless computer networks

2000-07-12

2004-06-22

Olms, Douglas (Department: 2661)

Multiplex communications

Data flow congestion prevention or control

Control of data admission to the network

C370S329000

Reexamination Certificate

active

06754176

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a scheme for managing transmission collisions among overlapping wireless computer networks.
BACKGROUND
Modern computer networks allow for inter-communication between a number of nodes such as personal computers, workstations, peripheral units and the like. Network links transport information between these nodes, which may sometimes be separated by large distances. However, to date most computer networks have relied on wired links to transport this information. Where wireless links are used, they have typically been components of a very large network, such as a wide area network, which may employ satellite communication links to interconnect network nodes separated by very large distances. In such cases, the transmission protocols used across the wireless links have generally been established by the service entities carrying the data being transmitted, for example, telephone companies and other service providers.
In the home environment, computers have traditionally been used as stand-alone devices. More recently, however, there have been some steps taken to integrate the home computer with other appliances. For example, in so-called “Smart Homes”, computers may be used to turn on and off various appliances and to control their operational settings. In such systems, wired communication links are used to interconnect the computer to the appliances that it will control. Such wired links are expensive to install, especially where they are added after the original construction of the home.
In an effort to reduce the difficulties and costs associated with wired communication links, some systems for interconnecting computers with appliances have utilized analog wireless links for transporting information between these units. Such analog wireless links operate at frequencies commonly utilized by wireless telephones. Although easier to install than conventional wired communication links, analog wireless communication links suffer from a number of disadvantages. For example, degraded signals may be expected on such links because of multipath interference. Furthermore, interference from existing appliances, such as televisions, cellular telephones, wireless telephones and the like may be experienced. Thus, analog wireless communication links offer less than optimum performance for a home environment.
In co-pending application, Ser. No. 09/151,579, which is incorporated herein by reference, a computer network employing a digital, wireless communication link adapted for use in the home environment was described. That architecture included a number of network components arranged in a hierarchical fashion and communicatively coupled to one another through communication links operative at different levels of the hierarchy. At the highest level of the hierarchy, a communication protocol that supports dynamic addition of new network components at any level of the hierarchy according to bandwidth requirements within a communication channel operative at the highest level of the network hierarchy is used.
The generalization of this network structure is shown in
FIG. 1. A
subnet
10
includes a server
12
. In this scheme, the term “subnet” is used to describe a cluster of network components that includes a server and several clients associated therewith (e.g., coupled through the wireless communication link). Depending on the context of the discussion however, a subnet may also refer to a network that includes a client and one or more subclients associated therewith. A “client” is a network node linked to the server through the wireless communication link. Examples of clients include audio/video equipment such as televisions, stereo components, personal computers, satellite television receivers, cable television distribution nodes, and other household appliances.
Server
12
may be a separate computer that controls the communication link, however, in other cases server
12
may be embodied as an add-on card or other component attached to a host computer (e.g., a personal computer)
13
. Server
12
has an associated radio
14
, which is used to couple server
12
wirelessly to the other nodes of subnet
10
. The wireless link generally supports both high and low bandwidth data channels and a command channel. Here a channel is defined as the combination of a transmission frequency (more properly a transmission frequency band) and a pseudo-random (PN) code used in a spread spectrum communication scheme. In general, a number of available frequencies and PN codes may provide a number of available channels within subnet
10
. As is described in the co-pending application cited above, servers and clients are capable of searching through the available channels to find a desirable channel over which to communicate with one another.
Also included in subnet
10
are a number of clients
16
, some of which have shadow clients
18
associated therewith. A shadow client
18
is defined as a client which receives the same data input as its associated client
16
(either from server
12
or another client
16
), but which exchanges commands with server
12
independently of its associated client
16
. Each client
16
has an associated radio
14
, which is used to communicate with server
12
, and some clients
16
may have associated subclients
20
. Subclients
20
may include keyboards, joysticks, remote control devices, multi-dimensional input devices, cursor control devices, display units and/or other input and/or output devices associated with a particular client
16
. A client
16
and its associated subclients
20
may communicate with one another via communication links
21
, which may be wireless (e.g., infra-red, ultrasonic, spread spectrum, etc.) communication links.
Each subnet
10
is arranged in a hierarchical fashion with various levels of the hierarchy corresponding to levels at which intra-network component communication occurs. At a highest level of the hierarchy exists the server
12
(and/or its associated host
13
), which communicates with various clients
16
via the wireless radio channel. At other, lower levels of the hierarchy the clients
16
communicate with their various subclients
20
using, for example, wired communication links or wireless communication links such as infrared links.
Where half-duplex radio communication is used on the wireless link between server
12
and clients
16
, a communication protocol based on a slotted link structure with dynamic slot assignment is employed. Such a structure supports point-to-point connections within subnet
10
and slot sizes may be re-negotiated within a session. Thus a data link layer that supports the wireless communication can accommodate data packet handling, time management for packet transmission and slot synchronization, error correction coding (ECC), channel parameter measurement and channel switching. A higher level transport layer provides all necessary connection related services, policing for bandwidth utilization, low bandwidth data handling, data broadcast and, optionally, data encryption. The transport layer also allocates bandwidth to each client
16
, continuously polices any under or over utilization of that bandwidth, and also accommodates any bandwidth renegotiations, as may be required whenever a new client
16
comes on-line or when one of the clients
16
(or an associated subclient
20
) requires greater bandwidth.
The slotted link structure of the wireless communication protocol for the transmission of real time, multimedia data (e.g., as frames) within a subnet
10
is shown in FIG.
2
. At the highest level within a channel, forward (F) and backward or reverse (B) slots of fixed (but negotiable) time duration are provided within each frame transmission period. During forward time slots F, server
12
may transmit video and/or audio data and/or commands to clients
16
, which are placed in a listening mode. During reverse time slots B, server
12
listens to transmissions from the clients
16
. Such transmissions may include audio, video or other dat

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