Time division protocol for an ad-hoc, peer-to-peer radio network having coordinating channel access to shared parallel data channels with separate reservation channel Number:7,099,296 from the United States Patent and Trademark Office (PTO) owispatent

Title: Time division protocol for an ad-hoc, peer-to-peer radio network having coordinating channel access to shared parallel data channels with separate reservation channel

Abstract: A novel protocol for an ad-hoc, peer-to-peer radio network that provides collision-free channel access with an emphasis on improving geographic reuse of the frequency spectrum. The protocol of the invention is executed on the reservation or control channel, and provides a method for allocating data transactions on the data channels. The system of the invention utilizes multiple parallel data channels that are coordinated by a single reservation channel. The transceiver of the system employs two modems to solve the channel reliability issues with multiple channel designs, where one is dedicated as a receive-only modem for gathering channel usage information on the reservation channel. High quality voice, video and data may be transmitted. The reservation channel implements a time division multiple access algorithm with dynamic slot allocation. In a distributed manner, nodes determine geographic reuse of slots based on channel quality extracted from the modem. Signal quality calculations are used to determine the likelihood of a slot reuse causing destructive interference within a node's neighborhood. Requests for slot usage are compared with the known traffic pattern and accepted or rejected by nodes within RF signal range based on the signal quality calculations.

Patent Number: 7,099,296 Issued on 08/29/2006 to Belcea

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Inventors:	Belcea; John M. (W. Melbourne, FL)
Assignee:	MeshNetworks, Inc. (Maitland, FL)
Appl. No.:	09/846,479
Filed:	May 2, 2001

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Current U.S. Class:	370/338 ; 370/458
Current International Class:	H04Q 7/24 (20060101)
Field of Search:	370/338,343,345,347,348,436,437,438,441,442,443,445,461,462

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Primary Examiner: Pham; Chi
Assistant Examiner: Ly; Anh-Vu
Attorney, Agent or Firm: Karpinia; Randi L. Buczynski; Joseph J.

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Parent Case Text

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CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of co-pending application Ser. No. 09/815,157 filed on Mar. 22, 2001.

Priority of provision application Ser. No. 60/246,833, filed on Nov. 8, 2000 is herewith claimed.

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Claims

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What is claimed is:

1. A protocol for use in an ad-hoc, peer-to-peer radio system comprising a series of terminals where each said terminal is capable of making at least one of an outgoing call or receiving an incoming call, and where each said terminal comprising computer means, memory means for storing program software means therein, and where each said terminal is capable of being hop of a routing path connecting a call from a source to a destination, comprising: software means for said memory means of each said terminal, said software means comprising means for generating communications-information for transmission based on time-division messaging; said communications-information comprising a series of time frames (TM) each divided into a series of time slots (TS); said communications-information comprising at least one time slot in which control-channel (CC) messaging information is transmitted, and other time slots in which is transmitted channel data (CD) messaging information; each said time frame (TF) comprising a last time slot; said software means further comprising means for generating initial control communications-information in a respective said last time slot (LTS) of a respective said time frame (TF) indicating initial presence of a respective said terminal in order to start communicating with other said terminals.

2. The protocol for use in an ad-hoc, peer-to-peer radio system according to claim 1, wherein the length of each said time slot for transmitting said communications-information is equal to each other.

3. The protocol for use in an ad-hoc, peer-to-peer radio system according to claim 2, wherein said software means further comprises means for switching transmission of initial control communications-information from said last time slot (TS) to another, free, earlier time slot of a subsequent time frame (TF) in order to reduce the chance of collision with other said terminals also initially registering.

4. The protocol for use in an ad-hoc, peer-to-peer radio system according to claim 3, wherein said initial control communications-information in said last time slot (TS) and in said another, free, earlier time slot of a subsequent time frame (TF) are transmitted at a frequency F0.

5. The protocol for use in an ad-hoc, peer-to-peer radio system according to claim 1, wherein said at least one time slot (TS) for said control-channel (CC) information is transmitted at a first power level, and said other time slots (TS) for said data-channel(DC) information are transmitted at a second power level.

6. The protocol for use in an ad-hoc, peer-to-peer radio system according to claim 5, wherein said second power level is equal to or less than said first power level, whereby RF interference is reduced.

7. In a protocol for use in a network of terminals each having computer means, memory means for storing program, and software means therein, said software means of each said terminal comprising means for generating communications-information for transmission based on time division messaging, said communications-information comprising a series of time frames (TM) each divided into a series of time slots (TS); said communications-information comprising at least one time slot in which control-channel (CC) messaging information is transmitted, and other time slots in which is transmitted channel data (CD) messaging information, the improvement comprising: each said time frame (TF) comprising a last time slot; said software means further comprising means for generating initial control communications-information in a respective said last time slot (LTS) of a respective said time frame (TF) indicating initial presence of a respective said terminal in order to start communicating with other said terminals.

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Description

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BACKGROUND OF THE INVENTION

The present invention is directed to a novel protocol for an ad-hoc, peer-to-peer radio network system having coordinating channel access to shared parallel data channels via a separate reservation channel. This system is disclosed in copending application Ser. No. 09/705,588, filed on Nov. 3, 2001, entitled "Methods and Apparatus for Coordinating Channel Access to Shared Parallel Data Channels", which application is incorporated by reference herein in its entirety.

The network system having coordinating channel access to shared parallel data channels via a separate reservation channel of copending application Ser. No. 09/705,588 is directed to a network system, such as radio network, where each node, or radio terminal, of the network is capable of serving as a node or hop of a routing path of a call from another, or to another radio terminal. In that system, communication between nodes or radio terminals is achieved using Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol with the addition of multiple parallel data channels serviced by one reservation channel. By dedicating a separate reservation channel for the multiple parallel data channels, collision-free access by all of the competing nodes or terminals of the service group of the network is greatly reduced. Communications between terminals or nodes is set up by information exchanged on the separate reservation channel, which information includes all of the call set-up information such as data channel desired to be used for transferring voice, video or data, the desired power level of at least initial transmission, messaging such as Request-to-Send (RTS), Clear-to-Send (CTS), Not-Clear-to-Send (NCLS), Acknowledgment (ACK) for indicating reception of the transmitted call, Non-Acknowledgment (NACK) for indicating improper reception of the call, etc. In this system, in order to further ensure fast, adequate and collision-free transmission and reception, besides a primary modem typically provided with the transceiver of each node or terminal, a secondary modem is also provided which is dedicated to the reservation channel when the primary modem of the transceiver is occupied, such as when sending out data on a data channel. This system also provides for collision free transmission and reception between nodes or terminals by transmitting the reservation and data channels in time slots of time frames, with the information as to which time slot is to be used being included in the messaging transmitted by the reservation channel. Such a format not only provides collision-free transmission, but also allows for Quality-of-Service (QoS) for different types of Class-of-Service (CoS), Thus, not only may voice and video be transmitted, besides data, but voice and data transmission may be prioritized, so that when competing calls vie for a data channel, the delay-dependent voice or video transmissions will take precedence. This prioritization is accomplished by assigning prioritized calls for transmission in earlier time slots of a time frame.

The network system disclosed in U.S. application Ser. No. 09/705,588 ensures that every node or terminal of a service set of terminals has the most information regarding all of other terminals of that service set, so that the choice of data channel to be used, any required delay is transmitting the call, information on power level, and the like, are checked and updated by each terminal by a practically continuous monitoring of the reservation channel.

As explained above, the system disclosed in U.S. application Ser. No. 09/705,588 utilizes protocol that provides collision-free channel access, which also emphasizes improving geographic reuse of the frequency spectrum.

In U.S. Pat. No. 5,943,322--Mayer, et al., which patent is incorporated by reference herein, the radio system thereof is for use in battlefield conditions. The ad-hoc, peer-to-peer radio system of this patent does not have, nor require, a base station, as conventional cellular systems, personal communications system (PCC), and the like, require; instead, each radio terminal forming part of the ad-hoc, peer-to-peer radio system may alternatively serve as a base station, in addition to being an ordinary link terminal of the radio system, whereby, if one such terminal serving as a base station should for some reason become inoperative, another terminal may take over and serve as the base station. In this patent, personal voice communications is based on a time division duplex (TDD) technique in a code division multiple access (CDMA) system, is operated without a fixed base station, and is provided with simultaneous transmission of a communications channel and a control channel, each spread by different PN codes. The PN code facilitates restricting communications on the network to a particular voice-conversation mode and between identified radios. Transmissions are performed in a time division duplex manner in 62.5 milliseconds slots. One of the radios initiates transmission and maintains power control and time synchronization normally done by a base station. A network control station can voluntarily or by command transfer control of the network to any of the other radios on the network. Colliding transmissions from more than one radio require the radios to retry transmitting until one of the radios transmits in an earlier time slot. Conversational mode capability is provided by equipping the radio receivers with despreaders in parallel for permitting a receiving radio to separately despread the simultaneously transmitted signals all other radios on the network and responding to each radio transmission individually. Simultaneous voice and data communications can be accomplished by equipping the receivers with despreaders for discriminating voice and data information signals spread by different PN codes.

In commonly-owned provisional application Ser. No. 60/248,182, which application is incorporated by reference herein, there is disclosed an ad-hoc, peer-to-peer radio system for use as a stand-alone system that is also connected to a cellular network and/or PSTN. The ad-hoc mobile radio networking system thereof is capable of receiving and transmitting voice, data and video calls through any number of different types of telecommunication networks, such as the PSTN, the Internet, and the like, besides the cellular and next-generation cellular networks.

Past research has shown that conventional Carrier Sense Multiple Access (CSMA) algorithms experience diminishing returns when networks approach their ultimate capacity. The vast majority of current research centers on channel access algorithms that provide transmission capacity over a single shared medium. An example of this is the IEEE 802.11 wireless standard which employs a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) algorithm. All users within a Basic Service Set (BSS) share a common channel resource.

The ad-hoc, peer-to-peer radio system of the present invention is based on a transport-mechanism using a time division duplex (TDD) technique in a code division multiple access (CDMA) system. Time Division Duplex (TDD) is a way of maximizing the bits/hz/km2. Such a system not only may be used for providing commercial voice, but is also quite suited to both transmission and reception of data and video services. Time Division Duplex (TDD) systems are typically used for packet data systems, since they make much more efficient use of the available bandwidth, in order to deliver a much higher effective data rate to the end user. TDD is typically used in fixed wired solutions or point-to-point wireless systems because it has its own spectrum limitations. TDD systems, however, have not hitherto been deployed for voice systems.

Unlike the personal communication radio system of U.S. Pat. No. 5,943,322--Mayer, et al., the Time-Division Protocol (TDP) of the present invention does not care about the modem-type of access to radio spectrum, and is designed to work with or without a base station or gateway, since modem functionality is not part of the TDP of the present invention. The protocol of the present invention uses one control/configuration channel and three or more data channels, where communication between radio terminals is planned for preventing interference. Time synchronization is independent of the communication, whereby no collisions among terminals are possible for configuration data, excepting in the last time slot, and no collisions are possible in the data channels, as described above. The protocol of the present invention may transmit data and video, in addition to voice, since each is just another class of data

The system of the present invention is much more complex due to multiple, parallel data channels that are coordinated by a single reservation channel. In this system, a combination of CSMA/CA, TDMA (time division multiple access), FDMA (frequency division multiple access), and CDMA (code division multiple access) is used within the channel access algorithm. The transceiver used in the system employs two modems to solve the channel reliability issues with multiple channel designs, as disclosed in the above-described copending U.S. application Ser. No. 09/705,588. Specifically, the system dedicates a receive-only modem for gathering channel usage information on the reservation channel. The reservation channel operates a hybrid CSMA/CA and TDMA algorithm. The remainder of the protocol uses FDMA for the multiple data channels, and CDMA for multiple users on the same data channel. Reference is also had to copending, commonly-owned U.S. patent application Ser. No. 09/846,479, filed on May 2, 2001, entitled "Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System", which is incorporated by reference herein, in which there is disclosed an example of routing table messaging which may be used in the present invention.

SUMMARY OF THE INVENTION

It is the primary objective of the present invention to provide an ad-hoc radio system as part of an overall, larger cellular network, and/or as a stand-alone, independent system, in order to provide commercial use for providing voice, data and video communications between radio terminals of the radio system of the invention and between equipment outside the system of the invention.

It is also a primary objective of the present invention to provide an overall protocol for ad-hoc radio system not utilizing a fixed base station, whereby a connection path by which a call is made takes into consideration the power loss associated therewith, in order to determine the least-energy routing of a call for the particular service type being transmitted, such as voice, data or video.

The protocol of the present invention is based on a time-division duplex (TDD) plus code-division multiple access (CDMA) burst packet technology used within the channel access algorithm of the system of the present invention. This provides the improvements in throughput and reliability that are required to deliver high quality voice, video and data The reservation channel implements a time division multiple access algorithm with dynamic slot allocation. In a distributed manner, nodes determine geographic reuse of slots based on channel quality. Signal quality calculations are used to determine the likelihood of a slot reuse causing destructive interference within a node's neighborhood. Requests for slot usage are compared with the known traffic pattern and accepted or rejected by nodes within RF signal range based on the signal quality calculations. Additionally, the algorithm of the present invention readily provides for the mobility of nodes between geographic areas through the use of a special slot that is reserved for nodes without reservations. Nomadic nodes use this slot to locate a permanent slot to claim for their use. Once claimed, the collision free properties can be enforced to improve the reliability and throughput of messages generated by this node. This results in a maximal use of the spectrum within a geographic area.

The system of the present invention utilizes a method and algorithm which, in the preferred embodiment, is intended for an ad-hoc network system called "ArachNet", and is based on least-energy routing of calls from and between network radio terminals. In simple terms, the major component of the routing decision is to choose the route to the destination that uses the least amount of energy over the complete route. The major reason for this is that least-energy routing minimizes the radiated RF energy, in order to reduce interference between terminals. A consequence of this is that it creates the most efficient use of the power supply of the terminals. Routing tables based on this least energy routing a developed by the system of the invention, and stored at one or more radio terminals, which routing tables are transmitted and stored by other terminals forming part of the link by which a call is connected. An example of such a routing table is disclosed in copending, commonly-owned U.S. patent application Ser. No. 09/846,479, filed on May 2, 2001, entitled "Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System", which is incorporated by reference herein.

Variants or equivalents of the system of the invention are possible. There are a number of variants of this approach that would provide acceptable performance. These variants include tuning of each of the four access schemes--CSMA/CA, TDMA, FDMA, and CDMA. For example, the width of the time slots may be adjusted based on the specific network over which the protocol is executing. Performance of the network is very dependent on the number of parallel data channels which can be used. A balance exists between the capacity of the reservation channel to make data reservations and the capacity of the data channels to provide service. This balance is dependent on the underlying capabilities of the dedicated, reservations-channel modem that implements the protocol. The performance of the protocol is also dependent on the inclusion of the channel quality extracted from the channel. Accurate estimates of the signal strength translate into improvements in geographic reuse, which can be obtained by aggressive power control schemes. Another example is the use of advancements in the codes used within the CDMA portion. Codes which improve the cross-correlation performance of terminals which share a common data channel improve the throughput and reliability of the overall network performance.

The adaptive power algorithm of system of the present invention leads to improvements in the determination of RF radius for a given data rate. Increasing the data rate and reducing power promotes geographic reuse. Any loss in communication is easily compensated by our ad-hoc routing algorithms.

The channel access approach of the invention is equally applicable for subnets which include or do not include gateways. In the gateway approach, time is coordinated within the ad-hoc environment by the gateway. In the non-gateway approach, a distributed time algorithm provides acceptable performance. In general, gateways permit the creation of larger networks such as MAN's and WAN's.

While the protocol method of the present invention is disclosed with regard to an ad-hoc, peer-to-peer radio system, the protocol is equally applicable to any wireless LAN, wireline network, and the like, to which the method and system disclosed in copending U.S. application Ser. No. 09/705,588 may apply.

BRIEF DESCRIPTION OF THE INVENTION

The present invention will be more readily understood with reference to the accompanying drawings, wherein:

FIG. 1 is a logical flow chart showing the software structure of the protocol of the system of the present invention;

FIG. 2 is depiction of the time-division of the TDD protocol (AP) of the present invention showing the time frames thereof with separated time slots;

FIG. 3 is a depiction of the many terminals (AT) connected to a particular gateway of the system of the present invention connecting the terminals to an exterior network, with one particular AT entering the service domain thereof and the connection path thereof;

FIG. 4 is a depiction similar to FIG. 3, but showing the particular AT moving away from the gateway and other AT's, whereby disconnection or reconnection must be carried out;

FIG. 5 is a depiction similar to FIGS. 3 and 4, showing a gateway connecting the system to outside networks, which connection path does not require very high speed, and where the total energy for passing data along the route is minimized;

FIG. 6 is a depiction of the time frames (TF's) with time slots (TS's) of the protocol of the system of the present invention required for performing one hop between terminals (AT's) for a permanent link, in order to assure proper communication;

FIG. 7 is a depiction similar to FIGS. 3 5, but showing the connecting route between two AT's of a local link, in order to control power requirements of the AT's;

FIG. 8 is a graphical depiction showing an AT approaching a group of AT's and the closed triangular connection therebetween;

FIG. 9 is a graphical depiction similar to FIG. 8 showing the open triangular connection therebetween if the AT's experience power reduction, whereby connection is preserved via the intermediate AT with ensuing reduction in energy loss;

FIG. 10 is a graphical depiction similar to FIGS. 8 and 9 showing the perturbed power profile of the AT's and the connection therebetween after the lowering of the power of all of the AT's;

FIG. 11 is a graphical depiction similar to FIG. 10 and showing the closed triangular connection therebetween after one time frame after power perturbation; and

FIG. 12 is a graphical depiction similar to FIG. 11 and showing the open triangular connection therebetween after two time frame after power perturbation with the ensuing steadystate, energy-saving path-connection between the AT's.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of a better understanding of the description, the following definitions and abbreviations are hereby given:

Definitions

"Service Area of a Terminal"

The geographical area where the transmission of a terminal can be received at a level higher than environment noise.

"Receive Set of a Terminal"

The set of terminals located within the service area.

"Transmit Set of a Terminal"

The set of terminals containing one particular terminal within their service areas.

"Service Set of a Terminal"

The set of terminals that can receive the transmission of one particular terminal and can be received at that terminal (the intersection between the receive set and the transmit set).

"Simple Connection"

An abstract notion