WO2001011833A1 - High-speed wireless network with a reliable wireless low bit-rate channel - Google Patents

High-speed wireless network with a reliable wireless low bit-rate channel Download PDF

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Publication number
WO2001011833A1
WO2001011833A1 PCT/US2000/021304 US0021304W WO0111833A1 WO 2001011833 A1 WO2001011833 A1 WO 2001011833A1 US 0021304 W US0021304 W US 0021304W WO 0111833 A1 WO0111833 A1 WO 0111833A1
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WIPO (PCT)
Prior art keywords
channel
wireless
network
wireless channel
data
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Application number
PCT/US2000/021304
Other languages
French (fr)
Inventor
Surendar Magar
Adisak Mekkittikul
Mahesh Venkatraman
William Li
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Berkeley Concept Research Corporation
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Priority to US14761699P priority Critical
Priority to US14761799P priority
Priority to US60/147,617 priority
Priority to US60/147,616 priority
Priority to US09/513,367 priority patent/US6690657B1/en
Priority to US09/513,367 priority
Application filed by Berkeley Concept Research Corporation filed Critical Berkeley Concept Research Corporation
Publication of WO2001011833A1 publication Critical patent/WO2001011833A1/en

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    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00Details not covered by groups G06F3/00 – G06F13/00 and G06F21/00
    • G06F1/16Constructional details or arrangements
    • G06F1/1613Constructional details or arrangements for portable computers
    • G06F1/1626Constructional details or arrangements for portable computers with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W76/00Connection management
    • H04W76/10Connection setup
    • H04W76/15Setup of multiple wireless link connections
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W28/00Network traffic or resource management
    • H04W28/16Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
    • H04W28/18Negotiating wireless communication parameters
    • H04W28/22Negotiating communication rate
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W84/00Network topologies
    • H04W84/02Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10Small scale networks; Flat hierarchical networks
    • H04W84/12WLAN [Wireless Local Area Networks]

Abstract

A multichannel wireless network (60), methods for its operation, and system components are disclosed. The network is designed to facilitate high-bit-rate data communication within a home, office, or similarly constrained area. According to the described embodiments, at least two different types of wireless channels form the network infrastructure. A primary wireless channel is designed for relatively low bit rate, high reliability and network-wide communication. A secondary wireless channel is designed for relatively high bit rate communication, but with potentially lower reliability and shorter ranges. A base station (62) uses the primary wireless channel to configure and control operation of the wireless network (60), including configuring pairs of devices as requested for direct communication over the secondary wireless channel.

Description

HIGH-SPEED WIRELESS NETWORK WITH A RELIABLE WIRELESS LOW BIT-RATE CHANNEL

FIELD OF THE INVENTION

This invention pertains generally to local area networks, and more particularly to methods and apparatus for implementing a w n eless local area network

BACKGROUND OF THE INVENTION

The flow of a wide variety of electronic information w ithin the boundaries of a home or office has become a realitv in today's society What began perhaps with a simple voice telephone line connection to the outside w oi ld has expanded to include cable teieusion. digital television, telephone modems, satellite links, cable modems, ISDN ( Integrated

Services Digital Network) connections. DSL (Digital Subscriber Line) connections, local area networks, sophisticated security systems, intercom systems, miiiti-speaker "surround sound" entertainment, smart appliances and smart "houses", etc. New technology w ill almost certainly expand the future uses for information distribution within the confines of a house or office

With enough foresight, a new home or office can be equipped with w hat mav be literally miles of wiring, to allow flexible configuration of a home or office to receive and distribute several (or perhaps all) of these iorms of information. But once the alls are in place, adding wiπng for a new technology, repairing wiring already in place, or even moving existing equipment to a new desired equipment location with no "outlet", may be reduced to choosing between either expensive remodeling or unsightly wiring running along baseboards and window sills. Furthermore, because most of these technologies require their own particular wiring and signaling requirements, a variety of wall sockets and wiπng are required, all adding to the expense of construction and detracting from the aesthetics of the space. Other problems ith w ired net orks exist For example, meiging ot multiple differing networks for centralized control etc , requires expensive bridging or bridges may not be av ailable at all

To combat these pioblems, w ireless networks are now being designed foi home use Many of these networks work in the Industrial, Scientific, and Medical (ISM) band that exists at 2 400 - 2 4835 GHz A second possible ISM band exists at 5 725 - 5 850 GHz These bands allow unlicensed operation, as thev are "garbage" bands that are generally unsuitable tor commeicial broadcast use (microwave ovens, toi example, opeiate in the 2 4 GHz band) Although low-power, narrowband signals mav be jammed by the noise occurring in these bands, digital spread spectrum techniques can be used to effect useful bandwidth

The Federal Communication Commission has lecently created an Unlicensed National Information Infrastructure (U-NII) to further address the needs for wireless digital data communications, particularly for wireless transmission at a rate that can support multimedia U-NII released three 100 MHz bands for use 5 15 - 5 25 GHz, for indoor use only and at low power, suitable for short ranges such as within a room, 5 25 - 5 35 GHz, at an intermediate power for mid-range uses, and 5 725 - 5 825 GHz (overlapping the 5 7 GHz ISM band), at a highei power for use up to several miles U-NII power requirements are designed to encourage wideband uses over narrowband uses, by specifying an allowable transmit power formula that reduces maximum output power logarithmically as signal bandwidth is reduced

Within the ISM and U-NII band idth constraints, several network concepts have been designed, most notably the IEEE 802 1 1 format, the Bluetooth™ format, and the Shared Wireless Access Protocol (SWAP) developed by the HomeRF Working Gioup Each of these formats is designed for use in the 2 4 GHz ISM band IEEE 802 1 1 format allows for data rates of 1 million bits per second (Mbps), 2 Mbps, and 1 1 Mbps, uses either Frequency Hopped Spread Specti um (FHSS) 01 Dnect Sequence Spiead Specti um (DSSS) to ov eicome noise, and has an operational range of about 40 m SWAP allows for data rates of 1 or 2 Mbps, uses FHSS, and has an operational range of about 50 m Bluetooth rM format allows lor a 1 Mbps data rate, uses FHSS. and allows for several operational ranges, depending on the power "class" of the transceiv er, the mam applications for Bluetooth™, howev er, envision the lowest power class transceiver, which has about a 10 m range

In the IEEE 802 1 1 format, two operational modes aie possible Distributed coordination Function (DCF) mode implements an "ad-hoc" network structure In DCF mode, each transceiver uses Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA), i e , it listens for quiet on the channel before it transmits Figure 1 illustrates an CSMA CA "ad-hoc" network foπned with transceivers 20, 22, 24. and 26 Each transceiver can communicate with each other transceiver that is within its range, whenever the channel is not already m use Problems can aπse when two transceivers that are out of each other's range (e g , 20 and 26 in Figure 1 ) cannot detect each other's transmissions, and attempt to communicate simultaneously using the channel This system also functions poorly with time- cπtical information, such as multimedia or voice

The second IEEE 802 1 1 operational mode is Point Coordination Function (PCF) mode In PCF mode, one of the nodes serves as a central Access Point (AP) The AP polls other nodes, asking each if it has data to transmit Each node only transmits when permitted by the AP This mode is generally used when the nodes also connect to a wired infrastructure PCF mode is typically inefficient and poorly-suited to the transmission of time-critical information

SWAP is similar to IEEE 802 1 1 in many respects SWAP also provides two access models, a Time Division Multiple Access (TDMA) service for time-critical data, and a CSMA CA service for asynchronous data delivery SWAP can work as an ad-hoc network as shown in Figure 1 When time-critical services are in use, however, a Connection Point is lequired The Connection Point coordinates the TDMA ser ice such that sufficient bandwidth is leserved for the time-cπtical services This system's TDMA mode ov ercomes some of the problems of IEEE 802 1 1 , although bandwidth is moie limited Figure 2 illustrates the more structured wireless concept employed by Bluetooth™, as described in the Bluetooth Specification Version 1 OB, Nov 29, 1999 The Bluetooth™ unit of network service is termed a piconet, e g , 46, 48. 50, each of which comprises one master transceiver (28, 34, 40, lespectiv ely) and up to sev en slave transceivers Within each piconet, a FHSS channel and phase is established bv the master, unique to that master TDMA. is used with 625 microsecond timeslots, with the master communicating in even-numbered time slots In odd-numbered time-slots, the slave last addressed by the master is allowed to communicate Each time-slot, the frequency for the piconet is hopped to the next in the hopping sequence established by the master Slave transceivers follow the hop sequence for that piconet, communicating with the master when allowed by the master A scαtternet 52 is a group of piconets with overlapping coverage areas Because each piconet operates on a different FHSS channel, frequency conflicts are infrequent When conflicts do occur, each piconet may lose a single packet Although a single transceiver is allowed to be a mastei m one piconet and a slave in another (e g , transceiv er 34), or a slave in two piconets (e g , transceiver 38), effective dual-piconet operation can be difficult to establish and maintain, since the specification establishes that overlapping piconets shall not be time- or frequency-synchronized Furthermore, although a transceiver may have visibility in two piconets, this does not establish visibility between other transceivers in the overlapped piconets Each connection in each piconet allows only for communication between that piconet's master and one of its slaves This structured design has advantages and disadvantages over the other formats described. It provides rigid control that is useful for time-critical applications and "plug and play" operation, and allows for devices to exist in multiple piconets. Lower power requirements decrease interference between overlapping piconets. allowing each piconet to enjoy most of its potential 1 Mbps throughput. But range is limited to less than typical household dimensions, bandwidth is inadequate for multimedia, the structure forces communication only with the master (slaves cannot communicate with each other during their time slots), the number of active devices in a piconet is severely limited, and the structure can waste bandwidth because the master must use an entire time slot each time it gives permission for transmission.

SUMMARY OF THE INVENTION

It is recognized herein that many of the drawbacks of the prior art wireless networking concepts occur because of the diversity of communication needs that these systems attempt to meet with a single shared channel. Some data streams require real-time delivery and/or high bandwidths, and thus tax the resources of the channel. Other data streams may require relatively low bandwidth and can tolerate reasonable delay, but may require strong security and a highly reliable channel. Designing a system that can meet these needs with a single shared wireless channel typically results in operational inefficiency and increased cost for network devices that do not require high bandwidth. In the present invention, at least two types of wireless channels can exist within a wireless network. A primary wireless channel is used for overall control of the network (and preferably, low data-rate data communication) — this channel need not support a particularly high data rate, but generally should be reliable, secure, and have relatively high interference immunity. Secondary wireless channels can also exist within the network. Each secondary channel is preferably used for high data-rate communications, generally bet een a pair of network devices

This multiple channel approach can achieve several adv antages over prior art network designs For example, network contiol can be admmisteied from a single point (1 e , a base station or master device) Devices that do not need to communicate at high data lates can be designed to use the relatively low data-rate primary channel only, and can thus be built simply and cheaply On the other hand, a device that needs to communicate at high data rates can be dynamically allotted a dedicated subchannel tailored to those needs Although a multitude of secondary wireless links can be simultaneously active, contiol of these links is admmisteied through the primary wireless channel and can thus be centrally administered with high reliability And because separate secondary wireless channels can be activ ated tor specific wireless links, each such channel can be individually tailored to provide the needed data rate at a power and modulation that minimizes interference with other active channels In one aspect of the invention, a method for operating a wireless base station in a wireless local area network is disclosed This method comprises establishing at least one primary wireless channel between the base station and each othei de ice on the local area network The base station uses the primary wireless channel to configure two of the devices on the local area network for data communication over a secondary wireless channel The secondary wireless channel has a higher data rate than the primary wireless channel In a related aspect of the invention, a method for operating a wireless network device is also disclosed This method comprises communicating over a primary wireless channel with a wireless base station The method further comprises responding to commands issued over the primary wireless channel by the base station, including a command to configure the network device for communication over a secondary wireless channel with another wireless network device In another aspect of the invention, a wireless base station is disclosed The base station comprises a data modulatoi /demodulator capable of communicating digital data with other wireless network dev ices over a pπmary ireless channel The base station also comprises a primary wireless channel control managei This managei issues contiol messages to other wireless network devices via the data modulator/demodulator and the primary wireless channel The base station further comprises a secondary wireless channel manager to allocate usage of a secondary wireless channel among the wireless network devices The secondary wireless channel manager also communicates with other w ireless network devices via the data modulator/demodulator and the primary wireless channel In yet another aspect of the invention, a wireless network device is disclosed. This device comprises a data modulator/demodulator capable of two-way data communication with a base station over a primary wireless channel This device further comprises a data modulator capable of transmitting data over a secondary wireless channel having a higher data rate than the primary wireless channel. The device also comprises a channel access control manager coupled to the modulator/demodulator to receive channel control data from the base station The manager configuies the data modulator to operate on the secondary wireless channel in response to channel control data received from the base station

In a further aspect of the invention, a wireless local area network is disclosed. The local area network comprises at least two wireless netwoik devices, each device capable of two-way data communication using a primary wireless channel At least one of the devices is also capable of transmitting data over a secondary wireless channel having a higher maximum data rate than the pπmary wireless channel At least one of the devices is capable of receiving data over the secondary wireless channel And one of the devices compπses a base station to communicate with each of the other wireless network devices over the pπmary wireless channel The base station uses the primary ireless channel to control usage of the secondary wireless channel bv the other dev ices

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments described below can be best understood with refeience to the di awing, wherein

Figures 1 and 2 illustrate pnor ait w ireless netw oik concepts, Figure 3 shows an exemplary deployment of w ireless network components in a wireless local area network according to one embodiment of the invention

Figure 4 shows one piotocol stack for a wireless base station operating over a primary wireless channel according to an embodiment of the invention,

Figure 5 shows one protocol stack for a wireless network device opeiating over both a pπmary wireless channel and a secondary wireless channel according to an embodiment of the invention,

Figure 6 shows a second protocol stack for a wireless network device, Figure 7 shows a high-level block diagram for a wireless netw ork dev ice capable of operating according to the inv ention within the framew ork of an existing phv sical w ireless standard,

Figure 8 shows secondary wireless channel connections for a partial wireless network employing wireless switches according to the invention, and Figures 9 and 10 illustrate high-level block diagrams for two wireless switch embodiments according to the invention

DETAILED DESCRIPTION OF THE EMBODIMENTS

Throughout the following descπption, several terms have defined meanings A band is a range of available RF frequencies, although the range need not be contiguous in frequency As used herein a channel is a communication channel or subchannel that uses RF tiansmission methods to conv ey digital information A channel is not limited to anv particular modulation scheme T o channels can be arranged to be substantial non- tntei fet ing by arranging them in separate, substantially non-overlapping ranges of frequencies (e g , two narrowband channels, or two FHSS channels using offset or different pseudorandom hopping sequences or phases), but those of ordinary skill will appreciate that substantial non-interference can be achiev ed m many other ways, such as by time-div ision multiplexing, code-div ision multiplexing (e g , DSSS), or combinations of sev eral or all of these techniques A LD (low data-rate) dev ice has the capability to communicate only on the pπmary wireless channel A HD (high data-rate) device has the capabilitv to communicate on both the primary and at least one secondary wireless channel

The description below focuses on a new wireless local area network infrastructure It is recognized herein that, among other things, the following properties are desirable in a wireless network for home or small office use (1) the ability to serve secure channel devices,

(2) the ability to serve relatively low bit-rate devices,

(3) the ability to serve relatively high bit-iate devices, requiring up to tens of megabits per second and even higher data rates,

(4) the ability to avoid interference sources, (5) reliable, secure network control, management, and configuration, and

(6) an ability to communicate using various protocols

The disclosed embodiments can operate within a network offering manv, or in some cases all, of these capabilities When implemented according to the following descπption, the preferred embodiments can provide an infrastructure backbone supporting a high-data- rate universal radio interface for almost any type of digital data, including the types identified in the background of the invention This lnfrastiucture is suitable for household use, office use, and other en ironments with similarly-limited network extent Various other advantages of these embodiments will be detailed below

The networking infrastructure described herein uses multiple types of w ireless channels to provide desired network functionalitv This includes at least one low bit-rate channel that is designed for high reliability This channel is used to provide control communications between the various devices served by the network This channel may also provide a low bit-rate data path for networked devices At least one high bit-rate channel can also exist within the network The high bit-rate channel can provide the data transfer capability needed for video, graphics, and high-speed data communications As compared to the low bit-rate channel, the high bit-rate channel generally achieves high data transfer rates at the expense of range, security, interference immunity, and/or overall reliability

In order to serve high bit-rate devices, a wireless RF channel operating in a GHz band (such as one of the ISM bands or the low-power U-NII band) is generally required But signals in these bands fade extremely rapidly due to absorption Thus it can be difficult to implement a high data late, highly reliable channel o er any appreciable distance in one of the GHz bands Thus in the examples below, the channel characteristics used for control communications differ from the characteristics of the channel used for high bit-rate data transfer The present disclosure presents three related exemplary approaches for providing both high data-rate and high-reliability, long-range wireless communication In the first approach, a primary, relatively low bit-rate channel is implemented using an RF channel, e g , in the 900 MHz ISM band (or a similar band), while secondary, relatively high bit-rate channels are implemented using one of the GHz bands Preferably, primary channel reliability and range are enhanced, e g , by spread spectrum modulation and or by incorporating strong error correction coding into the signaling scheme In the second approach, a primary, relatively low bit-rate channel and a secondary, relatively high bit-rate channel are both implemented using one of the GHz bands, with at least the pπmary channel using spread spectrum modulation and/or strong error correction coding Primary channel and secondary channel transmission can overlap in time, as long as the signals are substantially non-overlapping For instance, the two channels can use different DSSS spreading codes with a common RF carrier frequency, with the primary channel having a substantiallv highei chip late than the secondary channel due to the primary channel's lower bit rate The thud approach is similar to the second, except that the two channels are time-division multiplexed onto the same physical carrier and are logically separated by the receiver Except where specified below , the operational concepts described below apply to all three approaches

The relatively low bit-rate wireless channel (also described below as the "NO" channel) acts as a primary network communication channel The pioperties that will generally be optimized for the NO channel include interference immunity, reliability, ease-of- use, and data security As described above, relatively low RF carrier frequencies, low bit-rate modulation, strong error correction coding, and/or high process gain spectrum spreading can be used to optimize the NO channel Additionally, the NO channel typically employs data encryption and user authentication since computational constraints are low at NO data rates (e g , several hundred kbps) The NO channel capabilities are imbedded in all network devices, both LD and HD

In LD devices, the NO channel is used to distribute control information and data Some examples of LD devices are security devices (e g , window/door contacts, motion sensors, etc.), some audio devices (e g , audio players and speakers), and communication devices (e g , telephones, intercoms) The lelativelv high bit-i ate wireless channel (also described below as an N3' channel) acts as a secondaiv netw oi k communication channel The 3 channel is optimized for streaming infoimation at lelativ elv high data rates iiom one HD device to anothei HD device For instance, an N3 channel will generally use a high RF carrier trequencv to allow high data rate transmission High bit-rate modulation (l e , high bps/Hz) is also generally preferred, even if this lowers the channel's reliability somewhat Short phvsical ranges of opeiation can also be specified for HD dev ices, with repeaters and/or switches used to extend range

An N3 link can be a one-wav, peer-to-peer connection between tw o HD dev ices A two-way channel can be created by placing both an N3 tiansmittei and an \3 lecen ei at each HD device and configuring a two-way channel between them

Each HD device also incorporates an NO link, with N3 links being undei the control of the NO nk

A variety of HD devices may exist within the network Some examples are television set-top boxes, audio/video servers, computer servers, television receivers, digital video players, gaming consoles, and remote computer terminals For example, a \ ideo plaver can be configured to transmit on an N3 channel, and a nearby television receiv er can be configured to receive on that N3 channel

Figure 3 depicts an exemplary home or small office network 60 according to an embodiment of the invention A base station 62 communicates with each of devices 64 66 68, 70, 72, 74, 76, 78, and 80, using an NO channel to control each device's access to the network's channels

Devices 64, 66, and 68 are LD devices, which communicate only over the NO channel with the base station Thus in addition to using NO for control, any data communication involving an LD device will occur with that device peered to the base station Devices 70, 72, 74, 76, 78, and 80 are HD dev ices, each capable of communicating ov er at least one N3 channel in addition to the NO channel Although such dev ices mav still communicate low bit-i ate data ov er the NO channel to the base station each can also ti ansmit and/oi receive high bit-rate data over an N3 channel w ith a peei that is not necessarily the base station

Figure 3 shows sevei al ways in which the N3 channel(s) can be used Dev ice 70 is an N3 receiving (RX) node and device 72 is an N3 transmitting (TX) node Base station 62 has peered devices 70 and 72 in a one-way N3 link from the TX node to the RX node — such an operating mode is useful, e g , when device 72 supplies video or other graphical content and device 70 displays such content Base station 62 is also shown itself as a two-way N3 peer to device 74 Although, strictly speaking, the base station need not be capable of N3 operation itself, base station may be, e g , physically connected to a computer oi other device that provides high data-iate services to other dev ices such as de ice 74 as lllusti ated \ o sho n aie two HD devices 76 and 78 that wish to communicate This communication is facilitated by having each of the two devices communicate with de ice 80, which in this instance can be either a wireless repeater oi a w u eless switch This configuration is useful, e g , where devices 76 and 78 are out of direct N3 range of each other, or where devices are constrained from direct communication by network topology

Establishment of an N3 channel in the network of Figure 3 can proceed as follows A user first initiates a request for a connection between two devices For instance, a user's N0- capable menu-driven control device responds to the user's selection of a DVD player's output to a television receiver The control device's response includes forwarding a request over the NO channel to the base station The base station interprets the command, and checks the current status of the DVD player and the television receiv ei using the NO channel If the N3 link associated with either device is busy, the base station can resolve the request bv either terminating the pre-existing connection and establishing the new connection as requested, or by denying the newly-requested service When the connection is granted, the base station sends an affirmative message to the user's control device, when the connection is denied, the base station sends a negative notification instead When a connection is granted, the base station uses the NO channel to program the N3 transmit and receive devices for communication over an N3 channel The DVD playei then tiansmits v ideo data packets to the television receiver over the N3 channel

The base station s control of N3 channels can involve various degrees of sophistication For instance, prior to establishing a link between two N3 nodes, the base station can command the two nodes to send, receive, and report on the receipt of test signals in order to test the wireless channel conditions This can involve testing and reporting the potential channel's bit-error rate for known test bit sequences, under one or more power settings, frequency bands, modulation schemes, etc Based on the test report and other information known to the base station (such as the parameters for other N3 channels granted by the base station), the base station selects a set of N3 channel parameters that best fits the needs of the two N3 nodes and the needs of the network as a whole For example, if a suitable narrowband modulation scheme would require a high-power setting, the base station could opt to institute a lower-power (but higher bandwidth) spread spectrum channel that creates less interference with other N3 channels already granted The base station can also monitor the status of each N3 link For instance, the receiving N3 node can report packet corruption rates or signal loss to the base station over the NO channel When a problem is detected, the base station can then attempt to improve the channel For instance, if interference appears in the allotted frequency band, a new frequency band command can be sent to both the transmitter and the receiver Because the base station has a global picture of N3 channel usage, the base station can effectively administer frequency bands, time slots, power settings, and/or spreading codes to be used by each separate N3 link. The coordination of network management in the base station also allows the base station to implement sophisticated network management software without the necessity for similar complexity in other network devices. And since the NO channel itself is secure, reliable, interference-resistant, and relatively long-range, the basic network does not easily break down.

Figure 4 shows one exemplary communication stack 90 for a base station operating according to an embodiment of the invention. An NO channel physical layer (PHY) 92 comprises the RF link for the NO channel, e.g. a spread spectrum modulator/demodulator and RF transceiver operating at a relatively low data rate. NO channel media access controller (MAC) 94 and logical link controller (LLC) 96 provide link layer services for the NO channel. NO channel control manager 98 provides the control functions of the NO channel. These services include admission of new devices to the network, scheduling usage of the NO channel by each network device, and delivery of N3 channel control messages between N3 channel manager 100 and HD network devices.

N3 channel manager 100 coordinates usage of the N3 channel by the network devices. Channel manager 100 communicates, via the NO channel, with N3 channel access control managers located within the HD network devices. Channel manager 100 accepts requests for N3 channel creation, either from higher-layer applications or from other wireless devices, and issues commands to the appropriate network nodes, e.g., as detailed in the preceding description, to control N3 channels. Channel manager 100 also maintains state for the granted N3 channels, and may periodically check the status of each granted channel and update state. Channel manager 100 can dynamically alter the network's N3 channel configuration to lespond to changing conditions, such as interference or changes in overall N3 channel demand

In addition to the control path provided by managers 98 and 100, a traditional data path is provided, e g , bv IP layei 102 and TCP layer 104 IP v ei 102 w ill t picallv include a routing capability for routing IP packets from one network device to another over the NO channel, since in the preferred configuration each network device communicates ov ei the NO channel only with the base station In addition, applications 106 residing on the base station can use the TCP/IP path (or other similar paths, not shown) to interact with netwoik devices over the NO channel Figure 5 shows one exemplary communications stack 1 10 for an HD device operating according to an embodiment of the invention NO channel PHY 1 12, MAC 1 14, and LLC 1 16 provide the basic NO link to the base station NO channel contiol manager 1 18 , ιo\ ides the higher-level functions that allow the NO link to be established and controlled fiom the base station In addition, manager 1 18 provides message delivery for N3 channel access control manager 128

A parallel lower stack section provides an N3 channel PHY 130, MAC 132, and LLC 134 These blocks operate using the N3 channel within the parameters granted by the base station

Channel management controls 120 enforce the service granted by the base station Controls 120 accept input from NO channel control manager 118 and N3 channel access control manager 128, and use these inputs to respectively control the NO and N3 channels For instance, controls 120 can modify modulation schemes, frequencies, PN sequences, power settings, and/or transmit timing to agree with the service granted by the base station IP layer 122 resides in the NO stack and in the N3 stack Preferably, IP laver 122 selects an N3 path for delivery of a data packet over a parallel NO path when an N3 path exists

Figure 6 illustrates an alternate stack arrangement that is useful because it allows both NO and N3 to share access to a phvsical channel In this example the phvsical channel is an IEEE 802 1 1 -compatible (see background of the invention) channel Although the 802 1 1 PHY 142 and 802 1 1 MAC 144 aie compliant 802 1 1 receiv eis. thev contain additional functionality that allows for logical separation of NO and N3 transmit channels w ith TDM controlled by the base station Essentially, this functionality selects a first 802 1 1 -compliant transmit bit rate for NO packets and a second, higher 802 1 1 -compliant transmit bit rate for N3 packets The network operates in the 802 1 1 PCF mode Transmit parameters are selected for each logical channel Channel management control 160 sets the appropπate parameters for MAC 144 and PHY 142

802 2 LLC 146 implements an IEEE 802 2-comphant logical link control sublayer This sublayer recognizes and separates incoming N0/N3 control tiarfic from data tiatfic

LLC 146 also interleaves outgoing NO and N3 traffic as instructed by channel management control 160 The remaining blocks function similai lv to then counterparts in Figure 5

With stack 140 of Figure 6, the potential also exists for 802 1 1 communication with a wireless device that does not recognize the N0/N3 control layer Figure 7 shows a high-level block diagram for a network device 170 that can also communicate with a "non-network" (meaning non-N0 N3 network) device PHY 172 and MAC 174 receive both network and non-network packets over an 802 1 1 physical link Network packets are identified by the presence of an N0 N3-specιfic header, non-network packets have no such header When a network packet is received, it is passed up to N0 N3 filter 176, which strips and interprets the N0/N3-specιfic header If the header indicates that the packet is a network control packet, the packet is sent to N0/N3 channel control manager 178 for processing If the header indicates that the packet is a data packet, the packet is passed up to upper lavers 180 And when a non- netwoik packet is received, it is passed up to upper layers 180 without further processing

Fι i outgoing network data and control, N0/N3 filter 176 adds the N0 N3-specιfιc header appropriate for each packet prior to submission to MAC 174 The filter can be implemented in several stack locations, e g , between MAC and LLC, between LLC and network, between network and transport, or above transport Implementations at lower stack locations are preferred in order to reduce latency in the control connection

Any one of several different mechanisms can be used to facilitate communication between network and non-network devices First, small contention intervals can be included in the base station's TDM plan to allow a contention-based device to access to the physical channel These contention intervals can be used by non-network devices, as well as by network devices if allowed Network devices can also be granted (e g , upon request) time slots to communicate with a non-network device Preferably, the TDM plan remains flexible enough to accommodate the addition of non-network traffic of variable length

Turning now to another aspect of the invention, it is recognized that the NO or pπmary channel may allow reliable communication over a much larger area than the N3 or secondary channels N3 device-to-device coverage area may be constrained by transmit power limitations, multi-path delay spreading, blocked paths, and contention To combat these problems, N3 coverage can be extended using network devices that function as w ireless switches

Figure 8 illustrates a partial network 190 according to an embodiment of the invention, with the base station, LD devices, and NO links omitted for claπtv Switches 192, 194, 196, and 198 connect via N3 links to form a high-speed backbone netwoik HD devices 200, 202. 204, 206, and 208 are wireless network "leaf nodes", each connected to one of the switches

The configuration illustrated Figure 8 benefits the leal nodes m se eial icspects First, each leaf node's effectiv e lange toi high-bandwidth data communication is extended, while avoiding multi-path and keeping transmit power low Second, each leaf node can communicate with several different HD nodes concurrently, while maintaining only one N3 link (to the switch assigned to it by the base station) And third leaf nodes become less location-sensitive, since the switch deployment can provide a relatively uniform coverage for a wide variety of HD device locations From a network standpoint, several benefits are also achievable First, iehabihty can be improved by providing path diversity For instance, switches 192 and 194 shaie a direct N3 link, but if this link goes down, data can still be routed between switches 192 and 194 via switch 196 Second, scalability is improved, since network capacity can generally be increased and connections deci eased by the addition of more switches And third, because the base station still uses the NO channel to configure the network, N3 physical channel usage can be optimized on a network-wide basis under central control, with no dependency on N3 links necessary to administer the network

Figure 9 shows a high-level block diagram for one embodiment of a wireless switch 192 according to the invention Switch 192 comprises air interface circuiti v and MAC resources to support a plurality of wireless links The links can be configured to be substantially non-overlappmg by frequency division multiplexing, time-division multiplexing, code-division multiplexing, or by a combination of these techniques The air interface circuitry comprises a modulatoi and/or demodulatoi foi each u π eless link The an interface circuitry can also comprise a separate RF transmitter, receiver, or transceiver for each link In the alternative, multiple air interface circuits can share a common RF circuit Switch control is accomplished via NO channel air interface/MAC circuitry 210 Circuitry 210 allows a base station to communicate w ith NO channel control manager 212 and N3 channel access contiol manager 214, in essentially the same manner as the base station controls other network dev ices The pπmai y difference hen compared to the pieceding description is that N3 channel access control managei configures multiple channels (or subchannels) under base station contiol For instance, switch 192 is illustrated w ith one in/out pair of air interface circuitry (216. 218) configured for communication w ith a node A, second and third in/out pairs of an interface circuitry (220, 224, 226, 228) configured respectively for communication with a node B and a node C, a fourth incoming air interface circuit 230 configured to receive from node D, and a fourth outgoing air interface circuit 232 configured to transmit to node E

Packet switch 234 maintains a routing table that allows packets arriving at one incoming air interface to be routed to an outgoing air interface Routing table updates can be provided by neighboring s itches, and/or by the base station over the NO channel air interface 210 The operation of the switching core itself is w ell understood by those skilled in the art, and will not be detailed further

A modified version of packet switch 192 of Figure 9 can be advantageously deployed as a bridge to other types of networks For instance, Figure 10 illustrates a s itch/bridge 240 that provides three two-way network links, a HomeRF interface 242, and a 10/100 wired Ethernet interface 244 Packet switch/bridge 246 allows data to pass in and out of the network via interfaces 242 and 244

Those of ordinary skill will understand that v arious aspects of the embodiments described above can be combined in a large number of permutations Furthermore, many alternate implementations, functionally equivalent to those described herein, will become apparent to those of ordinary skill upon reading this disclosure Such permutations and alternate implementations are intended to fall w ithin the scope of the invention as claimed below

The preceding embodiments are exemplary Specific standards and pi otocols mentioned herein illustrate a few possible configuiations, the inv ention is applicable to configurations using alternate, additional, and or new standards and protocols Although the specification may lefer to "an", "one", "another", oi "some" embodιment(s) sev eral locations, this does not necessarily mean that each such refeience is to the same embodιment(s), or that the feature only applies to a single embodiment

Claims

WHAT IS CLAIMED IS
A method for operating a wireless base station in a wireless local aiea network, the method comprising establishing at least one primary wireless channel between the base station and each other device on the local area network, and using the pπmary wireless channel as a control channel to configure two of the devices on the local area network for data communication between the two dev ices over a secondary wireless channel, the secondary wireless channel having a higher data rate than the primary wireless channel
The method of claim 1, further comprising using the pπmary w ireless channel as both a control channel and as a relatively low data-rate, as compared to the data rate of the secondary wireless channel, data channel between the base station and another device on the local area network
The method of claim 2, further comprising forwarding data received on the pπmary wireless channel from one device on the local area network to another device on the local area network
The method of claim 1, wherein the primary wireless channel and the secondary wireless channel occupy at least partially-overlapping frequency bands, with at least the primary wireless channel using spread spectrum modulation to allow simultaneous use of both channels withm the local area network 5 The method of claim 4, herein both channels use spread spectrum modulation, further comprising modulating the pπmarv wireless channel w ith a laigei spiead g code than the spreading code used for the secondary wireless channel
6 The method of claim 1 , wherein the primary wireless channel and the secondary wireless channel occupy at least partially-overlapping frequency bands, the base station time division multiplexing transmission over the primary and the secondary wireless channels by the network devices
7 The method of claim 1 , further comprising using the pπmary wireless channel to monitor the status of the other devices on the local area network
8. The method of claim 1, further comprising admitting devices to the local area network using the primary wireless channel
9 The method of claim 1. further comprising encrypting data before placing that data on the pπmary wireless channel.
10. The method of claim 1 , further comprising authenticating each transmission received on the pπmary wireless channel
1 1. The method of claim 1 , wherein using the pπmary wireless channel as a control channel to configure two of the devices comprises, when the base station receives a request that requires establishing a secondary wireless channel between two network devices, using the pnmary wireless channel to check the status of each of the two network devices, and, when the status will allow the secondary w ireless channel to be established, using the primary wireless channel to program the two network devices for direct communication with each other over the secondaiv wireless channel
The method of claim 1 further comprising issuing a request ovei the primary w ueless channel to a pair of network devices that the two devices test channel conditions for a secondary wireless channel between the two devices
The method of claim 12 further comprising basing a grant of secondaiv w ireless channel bandwidth or power on the results of the channel condition test
The method of claim 1, further comprising monitoring the status of the secondaiy wireless channel, and instructing the two devices to change the parameters of the secondary wireless channel when the secondary wireless channel becomes unsuitable for the data communication needs of the two devices
The method of claim 1 wherein one of the two network devices is a wireless switch, the base station using the primary w ireless channel to set up multiple secondary wueless channels between the wireless switch and other network devices
The method of claim 1 , wherein one of the network devices is a wireless repeater that repeats signals received on a secondary wireless channel, the base station using the pπmary wireless channel to configure the repeating behavior of the repeater
A method for operating a first wireless network device comprising communicating over a primary w ireless channel with a wireless base station, and responding to commands issued ov er the primary wireless channel bv the base station to configuie the netwoik dev ice for direct communication over a secondarv w ueless channel w ith another wireless network device
18 The method of claim 17, wherein the first wireless device has the capability to communicate packet data over multiple secondary wireless channels, comprising at least one incoming and at least one outgoing channel as configured by the base station, further comprising maintaining a packet data routing table, and switching packet data fiom an incoming secondary wireless channel to an outgoing secondary wireless channel based on a companson of destination infoπnation contained in each packet to the packet data touting table
19 A wireless base station comprising a data modulator/demodulator capable of receiving digital data from and transmitting digital data to other wireless network devices over a primary wireless channel. a primary wireless channel control manager to issue contiol messages to othei wireless network devices via the modulator/demodulator and the pπmaiv ireless channel, and a secondary wireless channel manager to allocate usage of a secondary wireless channel among the wireless network devices, the secondaiv wireless channel manager communicating with other wireless network de ices via the modulator demodulator and the primary wireless channel The wireless base station of claim 19, wherein the data modulator/demodulatoi is capable of spread spectrum modulation
The wireless base station of claim 19, wherein the data modulator/demodulator uses error correction coding for communication over the primary wireless channel
A wireless network device comprising a data modulator/demodulator capable of two-way data communication with a base station over a pπmary wireless channel, a data modulator capable of transmitting data over a secondary wireless channel having a higher data rate than the primary wireless channel, a channel access control manager coupled to t e data modulator to receive channel control data from the base station, the manager configuring the data modulator m response to channel control data received from the base station
The wireless network device of claim 22, wheiem the data modulator/demodulator and radio frequency modulator share a common radio frequency transceiver
The wireless base station of claim 22, wherein the data modulator/demodulator is capable of spread spectrum modulation
The wireless network device of claim 22, further comprising a radio frequency demodulator capable of leceivmg data over the secondaiy ireless channel, the managei configuπng the radio frequency demodulator m response to channel control data received from the base station 26 A wireless local area netwoik comprising at least two wireless network devices, each device capable of two-way data communication using a primary wireless channel, at least one of the wireless network devices capable of transmitting data over a secondary wireless channel having a higher maximum data rate than the pπmary wireless channel, at least one of the wireless network devices capable of receiving data over the secondary wireless channel, one of the wireless network devices compπsing a base station to communicate with each of the other wireless network devices over the primary wireless channel, the base station using the pπmary wireless channel to control usage of the secondary wireless channel by the other devices
27 The network of claim 26, wherein at least one of the wireless network devices has the capability to communicate only with the base station using the pπmary wireless channel as both a control channel and as a data channel
28 The network of claim 26, wherein each communication over the pπmary wireless channel takes place between the base station and at least one of the other network devices
29. The network of claim 26, the pπmary wireless channel comprising multiple subchannels
30 The network of claim 26, the secondary wireless channel compπsing multiple subchannels, wherein the base station has the capability to assign one or more subchannels to a pair of the network devices for the purpose of direct communication between those devices
31. The network of claim 26, wherein at least one of the network devices further compπses a wireless switch having the capability to communicate over multiple secondary wireless subchannels including at least one incoming subchannel and at least one outgoing subchannel, the wireless switch capable of routing data wirelessly from a source network device towards a destination network device
PCT/US2000/021304 1999-08-06 2000-08-04 High-speed wireless network with a reliable wireless low bit-rate channel WO2001011833A1 (en)

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US14761799P true 1999-08-06 1999-08-06
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US60/147,616 1999-08-06
US09/513,367 2000-02-25
US09/513,367 US6690657B1 (en) 2000-02-25 2000-02-25 Multichannel distributed wireless repeater network

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