JP2008546354A - Control message management in physical layer relay equipment - Google Patents

Abstract

Relay device configured to selectively generate and transmit control message packets between radio stations (302, 304) on both the transmitting side (111) and the receiving side (112) of the relay device (100) (100). While the relay device (100) is relaying a signal from the transmission side (111) to the reception side (112), medium access control of the end-to-end protocol is performed to prevent other transmitters from transmitting in the network. Manage and manipulate the end-to-end protocol of control message packets in a way that does not change the (MAC) address. Control message management can also be applied to analog signal relay devices and digital relay devices such as inter-symbol or inter-packet relay devices where physical layer control message management is performed.

Description

  The present invention relates generally to wireless communications, and more particularly to a repeater configuration for improving wireless network performance by managing control messages to manage signal traffic.

  For example, as portable computer devices are becoming increasingly popular for unlimited access to broadband services, wireless local area networks (WLANs) described and defined in the 802.11, 802.16 and 802.20 standards ) And wireless metropolitan area networks (WMAN), there is an increasing need to extend the range of nodes such as access points associated with wireless networks. Efficient penetration of wireless networks is highly dependent on sustained performance and higher performance as user demand increases.

  The performance gap between actual and predetermined performance is the attenuation of the radiation path of radio frequency (RF) signals normally transmitted at a frequency of 2.4 GHz or 5.8 GHz in an operating environment such as an indoor environment. May occur. The base or AP to the receiver or client area is generally narrower than the required reach in a typical home and may be as short as 10-15 meters. Further, in a farm-style or two-story house, or a structure with a divided floor plane, such as a building made of a material capable of attenuating RF signals, the area that requires wireless coverage is, for example, 802 .11 physically separated by distances outside the scope of protocol-based systems.

  The attenuation problem may be exacerbated when there is interference in the operating band, such as interference from other 2.4 GHz devices or broadband interference including in-band energy. Furthermore, the data rate of devices operating using the standard wireless protocol depends on the signal strength. As the distance within the reach area increases, the performance of the wireless system usually decreases. Lastly, the structure of the protocol itself may affect the operating range.

  One method commonly used in the mobile radio industry to extend the range of radio systems is to use repeaters. In the case of a pure physical layer repeater, the random packet nature of typical WLAN protocols can cause various problems and complications because it does not provide a defined reception and transmission period. Because packets from each wireless network node are generated and transmitted spontaneously and cannot be predicted in time, undesirable results such as packet collisions may occur.

One system described in US patent application Ser. No. 10 / 516,327, a PCT national phase application based on international application number PCT / US03 / 16208, uses a frequency detection and conversion method to receive and transmit channels. By providing a separate relay device, many local transmission and reception problems are solved. By using the WLAN relay device described in the above U.S. patent, by converting a packet associated with one device at the first frequency channel to a second device using the second frequency channel. Two WLAN units can communicate with each other. Since the relay device operates as a physical layer device, the medium access control (MAC) address of the packet is not modified as in a relay device configured as a layer 2 device or a higher layer device. An indication associated with the conversion or conversion from the first frequency channel associated with the first device to the second frequency channel associated with the second device or from the second frequency channel to the first frequency channel is Depending on the real-time configuration of the relay device and the WLAN environment.

For example, the WLAN relay device monitors both frequency channels for transmission, and if a transmission is detected, the signal transmitted to the destination node is a signal received on the first frequency channel. It can be configured to convert to other frequency channels. It is important to note that the frequency translation repeater described in the above application operates in near real time to receive, boost, and retransmit packets.
US patent application Ser. No. 10 / 516,327

  When solving many problems in this field, the frequency conversion repeater described in US patent application Ser. No. 10 / 516,327 can be used, for example, when another transmitter is connected to the intended recipient. There is no control message management function, such as a function to modify the control message signal, to prevent sending an additional signal to the relay device while transmitting the modified signal. More specifically, the relay device cannot prevent other transmitters from responding to the correction signal while transmitting the correction signal.

  Therefore, one embodiment of the present invention provides a relay device for use in a wireless local area network. The relay device receives a signal on the first frequency channel and transmits a signal on a second frequency channel different from the first frequency channel, and demodulates a reception control message on the first frequency channel. And coupling with the transceiver to modulate one or more transmission control messages transmitted by the transceiver on at least one of the first frequency channel and the second frequency channel in response to the received control message Control message modulator / demodulator (MODEM). A transmission control message transmitted on the first frequency channel can be punctured to reserve the medium associated with the first frequency channel. The transceiver may include an amplifier for amplifying the control message. This amplifier has an associated gain that can be adjusted so that the control message can be punctured. Additionally or alternatively, an automatic gain controller can be provided so that transmission control messages transmitted on the first frequency channel can be punctured. The relay apparatus comprises a regenerative frequency conversion physical layer relay apparatus in which a transmission control message transmitted on the first frequency channel is punctured in the digital domain in order to reserve a medium related to the first frequency channel. be able to.

  Another embodiment provides a method for selectively modifying a message at a frequency translation repeater based on message parameters. The method includes the steps of searching for a preamble associated with a message received on a reception frequency channel, decoding a received message if a preamble is detected, generating a modified internal message, and a reception frequency. Transmitting a modified internal message on both the receive frequency channel and the transmit frequency channel to prevent further activity on the channel. The method also includes puncturing packets associated with the modified internal message transmitted on the receive frequency channel to reserve media associated with the receive frequency channel and prevent further activity thereon. be able to.

Another embodiment is a physical having a transceiver for receiving control messages on a first frequency channel and a transmitter for transmitting control messages on a second frequency channel different from the first frequency channel. A control including a layer repeater and an unmodified medium access control (MAC) layer transmitted on the second frequency channel to demodulate the control message received on the first frequency channel and achieve the purpose of the network A modulator / demodulator (MODEM) coupled with the transceiver is included for modulating a modified version of the message. The relay device, which may be a regenerative relay device or a non-regenerative relay device, converts the frequency of the modified control message signal from the first frequency channel to the second frequency channel, the access point (AP Achieve network objectives that can include one of connectivity limitations and predefined client prioritization.

  Yet another embodiment provides an end to end protocol (end to end) for selectively generating and transmitting control message packets between wireless stations on both the sending and receiving sides to achieve the purpose of the network. a physical layer relay device configured to manipulate the end-to-end protocol of the control message packet in a manner that does not change the protocol's medium access control (MAC) address.

  Other embodiments may be used between wireless stations on both the first segment and the second segment to ensure that the medium access control (MAC) level protocol functions properly between the first and second segments. A wireless relay device is configured to selectively generate and transmit control message packets.

  Finally, the purpose of the above summary is that the general public and especially scientists, engineers, and people in the field who are unfamiliar with the Patent and Trademark Office, patents and legal terms or phrases, Note that the nature and nature of the technical disclosure can be quickly determined. The summary is not intended to define the invention of the application (s) recited in the claims, nor is it intended to limit the scope of the invention in any way.

  BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, wherein like reference numerals designate identical or functionally similar elements throughout the several views, and which are hereby incorporated in and form a part of the following detailed description, the various drawings To further explain the various principles and advantages of the present invention.

  In the following, exemplary embodiments according to the invention will be described with reference to the drawings in which like reference numerals indicate like members. This specification is to further explain in a way that the best mode of carrying out the exemplary embodiments of the present invention can be performed, and to facilitate understanding and recognition of the principles of the present invention and its advantages, and any method However, the present invention is not limited.

  Furthermore, the use of terms such as first and second, etc., is intended only to distinguish one entity, item or behavior from another entity, item or behavior, such as Any actual such relationship or order between entities, items or actions does not necessarily and does not imply that. It should be noted that an embodiment may include a plurality of processes or steps that can be performed in any order, and is not necessarily limited to a particular order, unless otherwise specified. That is, processes or steps that are not so limited can be performed in any order.

When implemented, many of the features of the present invention, and many of the principles of the present invention, may be in conjunction with or within software, or a digital signal processor and software therefor, and / or an integrated circuit (IC) such as an application specific IC. Best supported. Those of ordinary skill in the art will likely require considerable effort and many design choices, for example due to uptime, current technology and economic considerations, but the concepts and principles disclosed herein. Would be able to easily generate such software instructions or ICs with minimal experimentation. Therefore, for the sake of simplicity and to avoid obscuring the principles and concepts according to the present invention as much as possible, the description of such software and ICs will be described with respect to the principles and concepts used by the illustrative embodiments. Limited to essential ones.

  FIG. 1 is a block diagram of an exemplary relay device 100. The relay device 100 that is a regenerative or non-regenerative relay device includes three basic components. The front end RF module or transceiver 110, the repeater module 120, and the processor 130. Preferably, the front end RF module 110, the repeater module 120, and the processor 130 are preferably implemented as separate chips, such as an ASIC, and preferably packaged together as a single chip set. The relay device 100 will be described using an RF signal-to-signal relay device. However, those skilled in the art will be able to perform control message management described below as a symbol-to-symbol relay device or a packet-to-packet relay in which physical layer control message management is performed. It will be understood that the present invention can also be applied to a digital relay device such as a device.

  The RF module 110, in a more general sense, each includes a first antenna 111 and a first antenna that can be considered as any type of electromagnetic transducer that can receive or transmit energy from / to the propagated signal. 2 antennas 112 are included. The RF module 110 is configured to transmit and receive signals through the first frequency channel A on the first antenna 111, for example, and to transmit and receive signals through the second frequency channel B on the second antenna 112, for example. The Note that throughout this specification the term “frequency channel” is synonymous with a more abbreviated term such as “channel” or “frequency”. Also, in a broad sense, it should be understood that the relay device can be configured to send and receive signals or messages through the first and second separate communication segments.

  The repeater module 120 includes a modulator / demodulator (MODEM) 121 such as 802.11 MODEM that is coupled in two directions to the RF module 110 by lines 113, 114, 115 and 116. The repeater module 120 may also have an analog control connection 122 that is coupled to the processor 130 through a data link, such as a data bus 123, and may be a series of analog connections.

  FIG. 2 is a more detailed schematic diagram 200 of the relay device 100 of FIG. 1, and more particularly a more detailed schematic diagram of the components included in the relay device module 120 in addition to the MODEM 121. The RF signals received by the antennas 111 and 112 are respectively filtered by the band filter 201 and input to the low noise amplifier (LNA) 204 through the switch 202. The signal is then mixed with the signals from the local oscillators LO1, LO2 at the mixer 205 to produce an intermediate frequency (IF) signal that is typically lower than the frequency of the RF signal. The IF signals are then input to splitters 206 that each operate to separate the IF signals in two separate paths. One of the paths from each splitter 206 couples the split signal to a delay line (in this case, a bandpass filter 208), while the other path couples the split signal to the power detector 210.

Each power detection device 210 is coupled to both the processor 130 and the variable gain amplifier (VGA) controller and state machine 212. The processor 130 and the VGA controller and state machine 212 are coupled to a MODEL 121 which is a splitter 206. In addition, VGA controller and state machine 212 is coupled to VGA 214 to control its gain. Outputs from the VGA 214 and the MODEM 121 are input to the mixer 215 through the IF switch 216 and mixed with the signals from the local oscillators LO1 and LO2.
The resulting signal is then amplified by power amplifier 218 before being output to one of antennas 111, 112 through switch 220 and one of switches 202.

  For details of the exemplary repeater, see US patent application Ser. No. 10 / 531,077 dated Apr. 12, 2005, the contents of which are incorporated herein by reference.

  The relay device 100 relays most of the 802.11 WLAN traffic in a transparent manner, but the relay device 100 operates at an access point (AP) and a frequency that serves as a lake. In order to facilitate associations between network nodes such as other devices linked by function (referred to as stations or STAs), some kind of 802.11 medium access control (MAC) procedure actively intervenes. Wake up.

  In the relay device 100, during an initialization sequence, such as a one-button push initialization procedure that occurs during several second button activation intervals, the relay device 100 selects available frequency channels and available APs. Scan and select the best every time, mainly based on channel signal quality and intensity. The MODEM 121 receives and generates network management messages from the AP and one or more stations, and the relay device 100 can generate a modified control message signal as described in more detail below.

  In order to be able to use “plug and play” in the network, the relay device 100 can generate and insert a modified control message in the network or can be used by the relay device 100. The modified control message can be sent simultaneously on both channels. Both methods have advantages and disadvantages. Simultaneous transmission of control messages is more efficient from the network point of view because it depends more on hardware but only requires fewer messages to be sent. The generation of the additional control message is performed using the existing hardware of the relay device, such as the Xtender ™ brand relay device commercially available from WIDEFI Corporation, the assignee of this patent application. be able to.

  However, the efficiency of the entire network is reduced because additional network traffic is generated. One of ordinary skill in the art can simultaneously transmit control messages over all repeater channels to reserve media by installing a splitter on the upconverter side of repeater 100 or for each outbound control message channel. It will be appreciated that it can be implemented in a variety of ways with only minor modifications to the hardware, such as by using separate transmit amplifiers. Therefore, simultaneous transmission does not require elaborate processing as is the case with the generation of additional control messages described in more detail below.

  As already explained, one method for inserting a control message that effectively merges the collision areas of the two channels selected by the relay device 100 during setup is to simultaneously send the necessary control messages by both frequency channels. How to send. That is, as soon as the relay device 100 detects a message, the relay device 100 transmits a control message simultaneously at the frequency at which the relay message is transmitted and at the frequency at which the message is received. When the relay device 100 transmits a message at the reception frequency, the energy on the reception frequency is transmitted by this other channel by carrier-sensing multiple access by other transmitters, for example, by a collision avoidance (CSMA-CA) protocol procedure. Prevents trying and acts as a hold-off procedure.

  Further, the relay device 100 also “punctures” the message transmitted at the reception frequency. That is, the relay apparatus 100 drops enough symbols from the packet so that the AP or the station receiving the packet can not use the packet. This “puncturing” of the message can be done in one of many ways, including reducing the gain of an amplifier in the repeater or an automatic gain controller in the repeater. Therefore, the message is processed but discarded by the receiving AP or station, thus occupying potential users at the receiving frequency while sending the modified message to the intended recipient on the transmission channel. Packets transmitted through the transmission channel are not punctured.

  One of ordinary skill in the art will appreciate the benefits derived from the above concepts and the concepts further described herein, and perform control message modification, holdoff and / or media reservation techniques. In order to understand that you can use several approaches in real hardware.

Hereinafter, an exemplary MAC layer management function of the relay device 100 and insertion of a specific control message for facilitating the function of the “plug and play” relay device will be described. The described MAC layer management functions include basic protocol, packet filtering, and media reservation. Each of these functions can be individually enabled or disabled, but in practice all are used.
Relay Device Operation Referring now to the table of relay device parameters listed in FIG. 1 and FIG. 9, during its initial configuration process, the relay device 100 is configured as an 802.11g channel frequency, referred to as channels A and B. Two channel frequencies are selected. The relay device 100 simultaneously monitors both frequencies and generates internal received signal strength indicator (RSSI) voltages (RSSI _A and RSSI _B ). These RSSI voltages are compared to RSSI threshold voltages RSTH _A and RSSH _B , which are dynamically adjusted by firmware running in the processor 130 that compensates for changing environmental conditions.

Whenever RSSI _A > RSSH _A , repeater 100 quickly configures itself as an RF repeater that converts the received signal on channel A into a slightly delayed frequency shifted copy on channel B To do. Similarly, when RSSI _B > RSSH _B , the signal received on channel B is relayed on channel A. This relay signal path is straight and is implemented entirely by an analog circuit such as the exemplary circuit of FIG.

At the same time, the relay of a new signal is started, and the relay apparatus 100 starts searching for the 802.11 preamble (direct sequence or OFDM) in the incoming signal. If the relay device is configured for “relay WLAN dedicated” mode (see parameter E _WLAN-ONLY ) and no valid preamble is detected within the timeout delay T _SEARCH , the relay device 100 A power amplifier, such as power amplifier 218 in FIG.

  As in the case of a single frequency WLAN, a collision may occur when an 802.11 node starts transmission while the relay device 100 is also relaying a signal on the same frequency. In fact, the relay device 100 combines the collision areas of both channels. Collision avoidance and recovery is managed by the standard 802.11 MAC protocol.

In one embodiment, the relay device 100 receives and decodes 802.11b / g frames encoded by 1 or 2 Mbps Barker Code Direct Sequence Spread Spectrum (DSSS) modulation. Such frames are simultaneously relayed and decoded.

  In addition to relaying received packets, the relay device 100 may be a dedicated version such as a modified version of a previously received beacon and a probe response frame, an acknowledgment (Ack) frame, or an XOS frame generated by the Xtender ™ relay device. An internally generated frame including the frame can be transmitted. While the internally generated frame is transmitted through one channel, relay device 100 does not relay a signal arriving through the other channel.

The relay device 100 generates RSSI comparator digital signals (CMPOUT _A and CMPOUT _B ) for each frequency. CMPOUT _A is asserted whenever RSSI _A > RSTH _A. The associated signal CMP _A is asserted whenever (a) CMPOUT _A is active, or (b) the transmitted signal is relayed from channel B whenever the relay device 100 is transmitting on channel A. It is asserted whether it is an internally generated signal or not. Otherwise, CMP _A is not active. The same situation applies to CMPOUT _B and CMP _B.

From CMP _A and CMP _B , the relay apparatus 100 _obtains two hysteresis filtering channel busy indicators SIG _A and SIG _B based on the hysteresis time T _HYST . The hysteresis time is the minimum time that CMP _X must remain in the same logic state before SIG _X switches to that state (X is A or B).

The sequencer that can be implemented by the VGA controller and state machine 212 of FIG. 2 also includes two _CTSs that are active when SIG _A and SIG _B each remain low for at least _TCTX. Compute (clear-to-transmit) indicators CTX _A and CTX _B.

  Note that the 802.11 MAC layer uses a much more complex clear channel calculation that relies on both RSSI and network allocation vector (NAV) channel reservation methods. Since the CTS logic of the relay apparatus 100 does not include the 802.11 MAC NAV mechanism, the probability that another station will transmit at the same time that the relay apparatus 100 transmits the modified packet is low. The relay device 100 does not detect the collision and does not attempt to transmit the collided packet.

  After the relay apparatus 100 finishes transmitting the internally generated frame through one channel, the relay apparatus waits for the RSSI comparator of the other channel to become inactive before relaying any signal. This “frame end relay suppression” function prevents the end of frame from being relayed that starts during transmission of an internally generated frame.

For example, assume that the relay apparatus 100 transmits a frame X generated internally through channel A. While frame X is being transmitted, the 802.11 node starts transmitting frame Y over channel B. Note that this 802.11 node cannot “listen” for transmissions from the relay device 100. When the frame Y continues beyond the end of the frame X, the end-of-frame relay suppression prevents the relay apparatus 100 from relaying the end of Y by the channel B when transmission of the frame X is completed.
Both beacons, probe responses and ACK handling beacons and probe response packets carry the current channel field indicating the 802.11b / g channel on which the AP is operating. For ease of explanation, it is assumed that the AP's beacon and probe response packet are relaying on channel B because the AP is tuned to channel A of relay device 100.

  In the relayed packet, the current channel field points to channel A, not channel B. Stations on channel B listening to the relay beacon packet ignore it. Because it indicates an incorrect channel. To provide a valid beacon to stations on channel B, relay device 100 transmits a modified copy of each beacon and probe response packet over channel B. Since a modified copy is sent after the original beacon or probe response frame is finished, the timestamp field must be modified to accommodate this extra delay.

  Beacon and probe response packet correction consists of two changes to the MAC payload. Initially, the current channel field in the “DS parameter set” is changed to point to the output channel number of the repeater. Next, the timestamp field is changed to reflect the actual transmission time of the modified packet. A new CRC-32 (FCS) value is inserted into the corrected frame. A corrected timestamp is generated by adding a time increment equal to the delay between beacon reception and corrected beacon transmission to the timestamp value in the received packet.

  The sequence number, source address (SA), and destination address (DA) fields in the MAC header remain unchanged. Therefore, the corrected beacon and probe response frames appear to have occurred at the AP. The power management field (eg, TIM field) also does not change if the time delay between the original frame and the corrected frame is assumed to be short enough to maintain the validity of the contents of the TIM field. It remains.

  Relay device 100 includes only one receive buffer for 802.11 beacons and probe response frames. The relay device 100 typically does not decode any new 802.11b frames that arrive while waiting for transmission of a corrected beacon or probe response frame associated with an earlier reception. The relay device 100 also includes multiple transmission buffers that can be used to generate ACK and CTS frames at any time. Therefore, the relay apparatus 100 can transmit the CTS packet through one channel while receiving the beacon or the probe response frame through the other channel.

Interoperability tests have shown that certain WLAN drivers may react in reverse to the presence of such relay packets that do not normally appear in a single frequency WLAN. Such “illegal” packets are relayed copies of uncorrected beacon and probe response packets when viewed by a station on the opposite channel that the AP used, and the opposite channel to the transmitting station's channel. It may include an ACK packet transmitted by a station that receives the corrected probe response packet as seen by the AP above. The impact of such “illegal” packet traffic varies greatly from manufacturer to manufacturer and from version within the driver series of the same manufacturer.
In order to mitigate the effects of “illegal packets”, relay device 100 is typically configured to prevent some frames from being relayed from one channel to another. Frame blocking is done in one of two ways: (1) truncation and (2) puncturing. In the case of an abort, a repeater power amplifier, such as power amplifier 218 in FIG. 2, is turned off in the middle portion of the packet for the remainder of the frame. In the case of puncturing, the power amplifier is turned off for a short T _PUNCTURE time in the middle of the MPDU, after which the rest of the frame is normally relayed. Turning off the power amplifier effectively stops transmission, so frames that are blocked by all listening nodes are received with a CRC-32 error. Although it is unlikely that a node located very close to the relay apparatus 100 will succeed in reception, it is possible.

  Under the IEEE 802.11 standard, APs in a BSS (“infrastructure”) network and all stations in an IBSS (“ad hoc”) network periodically transmit beacon packets at equal time intervals. To do. As is well known, the BSS network beacon protocol is a single frame transmission where the beacon packet is a broadcast packet.

  FIG. 3 illustrates that when the BSS network 300 and the relay device 100 process the beacon packet as shown in the figure when the beacon frame satisfies all the filter criteria described below, the AP 302 and the station 304 FIG. 6 is a corresponding packet sequence diagram that arbitrates between the two. A packet sequence diagram as shown in FIG. 3 is used to describe the protocol of the relay apparatus 100. The frame shown on the left side of the center line is transmitted by one channel (AP channel), while the frame shown on the right side is transmitted by the other channel (station channel). The protocol packet sequence proceeds from top to bottom. As shown in the figure, the end and the beginning of the relayed packet are connected by the received packet. This method should not be interpreted as a relayed packet starting after the end of the received packet. On the contrary, relay transmission occurs simultaneously with reception with only a short sub-microsecond delay between the two frames. Otherwise, except for such a relay packet, the length in the vertical direction is not an exact scale, but represents the time from the top to the bottom.

  As shown in FIG. 2, the original beacon at 306 is blocked as shown at 308, and as soon as the corrected beacon frame has a CTS condition of "true" on the channel of station 304, Internally generated and transmitted by the relay device 100 at 310. In this and subsequent figures, a large X at 306 indicates blocking of the relay frame by puncturing or truncation.

  In the standard 802.11 probe response frame protocol for BSS networks, if both the AP and the station are operating on the same frequency, the AP starts sending probe responses immediately after receiving the probe request. Or the AP can delay the start of the probe response frame if it has other higher priority traffic or if the channel is busy. The probe response is a unicast data frame. If the station successfully receives the probe response frame, the station immediately returns an ACK frame. If the station fails to acknowledge the probe response frame, the AP will send frames until it gets a return ACK or until it reaches the maximum number of retries (usually 4-7). try again.

FIG. 4 is a corresponding packet sequence diagram in which the BSS network 400 and the relay device 100 arbitrate between the AP 402 and the station 404. The relay apparatus 100 implements the following probe response protocol in order to process the probe response packet generated at 406 when the probe response frame satisfies the filter criteria described below. The relay apparatus 100 transfers the probe request generated at 408 by the station that has not changed to the AP 404 at 410. The AP 402 responds with a probe response frame at 406. As shown at 412, the relay device 100 prevents this probe response from going to the station 404 by puncturing or aborting it. When the relay apparatus 100 correctly receives the probe response frame, in 414, the relay apparatus 100 returns an ACK frame (ACK ₁ ) to the AP 402. The delay between the end of the probe response frame and the start of the ACK frame is specified by the firmware parameter T _PRACK as shown in the table of FIG. When the transmission possible condition on the station 404 channel is “true”, the relay apparatus 100 transmits the probe response frame corrected at 416. If the station 404 correctly receives the corrected probe response frame, the station 404 returns an ACK frame (ACK ₂ ) to the relay apparatus 100 at 418. As shown at 420, the relay device 100 prevents this ACK ₂ frame from going to the AP 402 by puncturing or aborting it. In this case, the relay apparatus 100 blocks any ACK packet whose reception starts between the TSTART _CPRACK and the TEND _CPRACK at the end of the corrected probe response transmission. The decision of the relay device to block does not take into account the MAC address in the ACK frame. When the relay device 100 does not correctly receive the ACK ₂ frame, the relay device does not retry the corrected probe response frame. Instead, if the station 404 does not correctly receive the corrected probe response frame, the station typically transmits another probe request frame.
The packet filtering relay device 100 applies three separate tests (source address, destination address, and current channel) to each received probe response packet. Two of these tests (source address filter and current channel filter) are also applied to each received beacon frame. Each of these tests corresponds to a “frame filter” that can be individually enabled or disabled (see the parameters in the table of FIG. 9, E _SAFILTER , E _DAFILTER , and E _CCFILTER ). If the filter is operational, the associated test determines whether the filter is in a passable or non-passable state. If the filter is inoperable, the state can be passed at any time. As will be appreciated by those skilled in the art, a repeater state machine, such as the exemplary VGA controller and state machine 212 of FIG. It can be configured by a processor.

When the relay device 100 receives the beacon frame B, the corrected beacon frame is transmitted only when both the source address and the current channel filter state can be passed for the received frame B. The When the relay apparatus 100 receives the probe response frame P, the probe response ACK (that is, ACK only) if the source address, the destination address, and the current channel filter state can all pass through the received frame P. ₁ ) and a correction probe response frame are transmitted.
In the exemplary embodiment shown in FIG. 2, the test definition relay device 100 is built into the VGA controller and state machine 212 and is typically the AP of the AP selected by the firmware during the configuration of the relay device. Contains an internal 6-byte MAC address register RXSRCMAC that is loaded with the address. A beacon or probe response frame passes the source address test only if the IEEE MAC source address is equal to the contents of the RXSRCMAC. The relay apparatus 100 stores the IEEE MAC source address of the last probe request packet received on a channel different from that used by the AP in the 6-byte internal register LPRQSRCMAC. The AP channel is defined by register settings loaded via firmware. The probe response frame passes the destination address test only if the IEEE MAC destination address is equal to the contents of the LPRQSRCMAC.

  In the exemplary embodiment shown in FIG. 2, the relay device 100 is built into the VGA controller and state machine 212 and specifies two 802.11g channels corresponding to the relay device channels A and B. Contains the current channel register. These registers are loaded by the processor firmware. A beacon or probe response frame passes the current channel test only if the current channel value is equal to the current channel register value corresponding to the channel (A or B) on which the frame is received.

  The above description focuses on the interaction between one exemplary AP and one exemplary station. In the more general situation where two or more APs respond to the same probe request packet, if source address filtering is inoperable, the relay device will correct the probe for each AP's probe response packet. Follow the response protocol. The station then makes a complete selection of the AP with which it is associated. If source address filtering is possible, the relay device 100 generates a corrected probe response only for the probe response carrying the specified source MAC address specified by the register RXSRCMAC, as already described. The designated source MAC address identifies the AP that is “affiliated” with the relay device 100. Therefore, the station sees at most only one AP probe response and is not associated with other APs that responded to that probe request.

Unrelated APs are processed as shown in the BSS networks 500, 600 of FIGS. As shown at 500 in FIG. 5, when the beacon frame is transmitted from the AP 502 to the station 504 at 506, the relay apparatus 100 does not generate the beacon frame shown at 508, and at 510. The correction beacon frame shown in FIG. In FIG. 6, when the station 604 generates and transmits a probe request to the AP 602 at 606, and when the AP 602 generates a probe response at 608, the relay device 100 indicates as indicated at 610. No probe response is relayed to, no ACK ₁ is generated as shown at 612, or no corrected probe response frame is generated as shown at 614. Thus, station 604 is unaware of the presence of AP 602.

  In order to completely mask non-designated APs, the relay device 100 also blocks any beacon frames received from such APs. The protocols of FIGS. 5 and 6 also apply to any beacon or probe response packet that does not match the applicable filter, respectively. Note that in FIGS. 5 and 6, a large X is used to indicate both relay frames that are never transmitted and puncturing / censoring of frames, as the comments in parentheses indicate.

The destination address filter prevents the relay device 100 from sending a corrected probe response within the situation where the probe request was sent by a node already operating on the AP channel. When a probe request is sent over the AP channel, the requesting node can hear the AP probe response directly, so no correction probe response is required. Current channel filters prevent repeater 100 from generating corrected beacons and probe response frames for packets generated by nearby nodes operating on adjacent channels. Direct sequence modulation used at 1 or 2 Mbps often allows adjacent channel reception.
Based on the above description of the relay device probe response protocol for an ad hoc network BSS network, a similar mechanism can be applied to an ad hoc network. More specifically, in an IBSS “ad hoc” network, beacons and probe response frames can be transmitted by any station in the network. Frame filtering by the source MAC address test is not compatible with such networks. This is because the relay apparatus 100 must immediately generate correction beacons and probe response frames for two or more source MAC addresses.

In the case of an IBSS network, the relay device 100 can use another method to load the LPRQSRCMAC register. When this method is used, the relay device 100 has the last probe received in the LPRQSRCMAC, whereby the relay device 100 has received a channel other than the channel on which most recent beacons or probe response frames were successfully received. Stores the IEEE source MAC address of the request packet.

For example, assume that relay device 100 most recently received a beacon or probe response over channel A and relay device 100 transmitted a corresponding corrected beacon or probe response frame over channel B. In that case, LPRQSRCMAC contains the source MAC address of the last probe request packet received by channel B. When the destination MAC address test can be performed, the relay device 100 transmits a future corrected probe response frame only to the destination MAC address that matches the LPRQSRCMAC. Current channel testing can be used for both BSS and IBSS networks. Note that the relay device configured with another destination MAC address test and the current channel test simultaneously support both BSS and IBSS operations.
Medium Reservation for Correction Beacon and Probe Response Frame As described above, when the relay apparatus 100 transmits an internally generated frame by channel A, the 802.11 node on channel B detects such transmission. It is not possible. Therefore, since the 802.11 AP or the station starts transmission of a frame through the channel B while the relay apparatus is transmitting through the channel A, the station on the channel B cannot hear this frame. This situation destroys the desired symmetry of channels A and B, where both channels share the same collision area.

  7 and 8, the relay device 100 uses the CTS frame addressed to the relay device 100, that is, the CTS frame transmitted by the relay device 100 and addressed to the IEEE MAC address of the relay device itself. Reserving the medium can alleviate this problem. In the case of the beacon protocol, this situation is indicated by the network 700 in FIG. More specifically, when the relay apparatus receives the beacon 706 transmitted by the AP 702, the relay apparatus does not transfer the beacon to the station 704 as indicated by 708. On the contrary, the relay apparatus transmits the self-addressed CTS frame generated internally at 710 to the AP 702 and transmits the corrected beacon generated internally at 712 to the station 704.

  In FIG. 8, in the case of the probe response protocol, the self-addressed CTS frame is inserted at 806 between the probe response ACK at 808 and the corrected probe response at 810. The use of such a self-addressed CTS frame is optional. Similar comments apply to similar situations of internally generated frames transmitted over channel B.

Referring again to FIGS. 7 and 8, although not shown in detail in the figures, the self-addressed CTS frame also aborts the relay beacon or probe response, and the self-addressed CTS by the channel of the station immediately after the breakpoint. By transmitting the frame, it can be transmitted by the channel of the station. In this situation, a self-addressed CTS is transmitted, while the end part of the beacon or probe response frame is still being received by the AP channel. The scheduling of such overlapping self-addressed CTS frames is another set of transmittable parameters that may differ from the parameters used to schedule other internally generated frames such as correction beacons and probe response frames. Controlled by Field tests suggest that overlapping self-addressed CTS frames on the station channel are ignored by most 802.11 products on the market. Currently, the transmission of overlapping self-addressed CTS frames starts slightly shorter than one distributed inter-frame space (DIFS) interval from the end of the aborted relay transmission, sufficiently covering the maximum length beacon frame at 1 Mbps It is believed that it is best to reserve media for the time to do.
XOS Packet Reception and Transmission An exemplary embodiment of a relay device 100, such as the Xtender ™ relay device described above, can also support the reception and transmission of dedicated Xtender Operating System ™ (XOS) management packets. . XOS packets facilitate communication between multiple Xtender ™ and other XOS aware APs or stations.

  According to an example embodiment, the relay device 100 automatically acknowledges all probe response messages from its associated AP. This is because the ACK from the station to the probe response is delayed beyond the ACK timeout window (8 to 12 microseconds) by the time when the relay apparatus 100 corrects and retransmits the probe response. . In addition to the relay device 100 that generates an ACK to the probe response, the ACK from the station is punctured on the way back to the AP in order to avoid confusion from an extra ACK. Since the relay apparatus 100 generates ACK for all probe responses, when the probe response is directed to a station on the AP channel, a collision occurs due to this ACK message on the AP channel.

  When both the relay device 100 and the station are listening on the AP channel, both the station to which the probe response is sent and the relay device 100 try to acknowledge the packet. Since these ACKs are not required to follow the clear channel estimation algorithm, both the station and the relay device 100 transmit ACKs at the same time (about 4 microseconds of each other) and collide ACKs. Therefore, the AP will never receive an appropriate ACK for a probe response sent to a station on the AP channel. This causes the AP to continue sending probe responses until it reaches its maximum number of retries. Some NIC drivers simply ignore the extra probe response packet, while other NIC drivers have been found to be very sensitive to any “abnormality” in MAC messaging.

  In order to solve the above problem, when the relay device 100 receives a probe request on the relay channel, the ACK response is filtered based on the MAC address so that the MAC address of the transmitting station is stored by the relay device. Can do. Therefore, the relay apparatus 100 acknowledges only the probe response received together with the destination MAC that matches the MAC from the probe request.

  To keep the implementation small, only the MAC address from the last probe request received is stored. However, for example, if two different stations send a probe request before the first probe request responding by the AP, only the MAC address from the second probe request is stored. The probe response to the first probe request is not an ACK by the relay device 100. In practice, this scenario seems unlikely. Therefore, the AP sends some probe response retries, and the station can send other probe requests if it wants to do so. In many cases, one station transmits a plurality of probe requests before receiving a probe response. In this case, the relay apparatus 100 acknowledges all the probe responses. This is because these probe responses are destined for the same MAC address.

Furthermore, ACK responses can be filtered based on listening for other ACKs. When the probe response is received on the AP channel, the relay apparatus 100 starts listening to the channel for the ACK from the station. If the ACK is not detected within a certain length of time, the relay device 100 generates an ACK for the probe response. The ACK timeout window for DSSS packets is 8-12 microseconds. This means that the transmission of the ACK to hear the signal within the window can be started at any time. How long the relay device 100 listens before generating its own ACK is not always easy. When the distance between the relay device 100 and the AP is represented by Dxa and the distance between the relay device 100 and the station is represented by Dxs, the detection time is set to 12 so that the ACK of the relay device falls within the timeout window. Microsecond-Dxa (feet) ^* Must be 0.001 microsecond or less. This means that when a certain station is delayed from this, the station collides with the normal repeater 100.

  For example, if the station is 500 feet away from the AP and 1000 feet away from the repeater 100, the repeater 100 cannot hear the ACK at all. However, when the relay device 100 acknowledges, the relay device 100 is located at a distance sufficiently close to the AP to cause a collision. Assuming that the relay device 100 has heard the ACK, the relay device 100 times out within 11.5 microseconds in order to retrieve the ACK in time. Therefore, the station must respond to the relay device 100 within 10.5 microseconds in order to hear the ACK in time because it does not transmit.

  The invention has been described in detail herein with particular reference to presently preferred embodiments. However, it will be understood that various changes and modifications can be made without departing from the spirit and scope of the invention.

FIG. 3 is a block diagram illustrating components of a relay device according to various exemplary embodiments of the present invention. FIG. 2 is a detailed schematic diagram showing components of the relay device module of FIG. 1. FIG. 2 is a packet sequence diagram illustrating a control message management function of the relay device of FIG. 1 operating in an 802.11 WLAN network associated with a beacon protocol. FIG. 2 is a packet sequence diagram illustrating a control message management function of the relay device of FIG. 1 operating in an 802.11 WLAN network associated with a probe response protocol. FIG. 2 is a packet sequence diagram illustrating a control message management function of the relay device of FIG. 1 operating in an 802.11 WLAN network associated with a beacon protocol including a failure filter. FIG. 2 is a packet sequence diagram illustrating a control message management function of the relay device of FIG. 1 operating in an 802.11 WLAN network associated with a probe response protocol including a failure filter. FIG. 2 is a packet sequence diagram illustrating a control message management function of the relay device of FIG. 1 operating in an 802.11 WLAN network associated with a self-addressed CTS including a modified beacon. FIG. 2 is a packet sequence diagram illustrating the control message management function of the relay device of FIG. 1 operating in an 802.11 WLAN network associated with a self-addressed CTS including a modified probe response. 2 is a table of configuration parameters for firmware that is programmed and run in the processor of FIG.

Claims (19)

A relay device for use in a wireless local area network,
A transceiver for receiving a signal on a first frequency channel and transmitting the signal on a second frequency channel different from the first frequency channel;
One or more of which the transceiver transmits on at least one of the first frequency channel and the second frequency channel in response to demodulating a reception control message on the first frequency channel and in response to the received control message; A control message modulator / demodulator (MODEM) coupled with the transceiver to modulate a transmission control message of
A relay device comprising: The relay apparatus according to claim 1, wherein the transmission control message transmitted by the first frequency channel is punctured to reserve a medium associated with the first frequency channel. The relay of claim 2, wherein the transceiver includes an amplifier for amplifying the control message, the amplifier having an associated gain adjustable to allow the control message to be punctured. apparatus. The relay device according to claim 2, further comprising an automatic gain controller coupled to the adjustable transceiver so that the transmission control message transmitted over the first frequency channel can be punctured. The relay apparatus includes a reproduction frequency conversion physical layer relay apparatus, and the transmission control message transmitted by the first frequency channel in the digital domain is punctured to reserve a medium related to the first frequency channel. The relay device according to claim 2 to be processed. A method for selectively modifying a message at a frequency conversion repeater based on a parameter of the message,
Searching for a preamble associated with a message received by the receive frequency channel;
Decoding the received message when detecting the preamble;
Generating a modified internal message;
Transmitting the modified internal message on both the receive frequency channel and the transmit frequency channel to prevent further activity on the receive frequency channel. 7. The method further comprises puncturing packets associated with the modified internal message transmitted by the reception frequency channel to reserve a medium associated with the reception frequency channel and prevent further activity thereon. The method described in 1. 8. The method of claim 7, wherein the step of puncturing a packet includes the step of puncturing the packet by adjusting to reduce the gain of the modified internal message transmitted by the receive frequency channel. 8. The method of claim 7, wherein the step of puncturing a packet includes the step of puncturing the packet by adjusting automatic gain control associated with the modified internal message transmitted by the receive frequency channel. The modulator / demodulator (MODEM) in the frequency conversion repeater is
A demodulator section for demodulating the received protocol message;
A modulator unit for modulating a modified version of the received protocol message including modified parameters for transmitting on both the first frequency channel and the second frequency channel. The MODEM of claim 10, wherein the modified protocol message transmitted by the first frequency channel is punctured or aborted. A physical layer relay device,
A transceiver for receiving a control message over a first frequency channel and transmitting the control message over a second frequency channel different from the first frequency channel;
A modified version of the control message at an unmodified medium access control (MAC) layer transmitted over the second frequency channel to demodulate the reception control message on the first frequency channel and achieve the purpose of the network A physical layer repeater comprising a modulator / demodulator (MODEM) coupled to the transceiver to modulate the signal. The purpose of the network is one of frequency modulation of the modified control message signal from the first frequency channel to the second frequency channel, access point connectivity restrictions, and client access prioritization. The physical layer relay device according to claim 12, comprising: The physical layer relay device according to claim 12, wherein the physical layer relay device includes one of a regenerative relay device and a non-regenerative relay device. Selectively generate and transmit control message packets between wireless stations on both the sender and receiver, without changing the medium access control (MAC) address of the end-to-end protocol to achieve the purpose of the network A physical layer relay device configured to operate the end-to-end protocol of the control message packet in a method. Control messages between radio stations on both the first communication segment and the second communication segment to ensure that the medium access control (MAC) level protocol functions correctly between the first and second communication segments. A wireless relay device configured to selectively generate and transmit packets. The one or more transmission control messages transmitted by the transceiver on the first frequency channel, either by the relay device puncturing or aborting the one or more transmission control messages The relay device according to claim 1, further comprising a physical layer relay device for interrupting the communication. The relay device of claim 1, wherein the relay device includes one of analog, RF, and digitally sampled relay devices. The relay device according to claim 1, wherein the relay device comprises a regenerative relay device in which the MODEM modulates one or more control messages according to unmodified packet addressing.

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