Wireless local area network repeater

Wireless LAN Repeater

Technical field

The present invention generally relates to wireless communication, and more particularly to a repeater for increasing the coverage area of a wireless network.

Background technique

Several standard protocols for wireless local area networks commonly referred to as WLANs are becoming increasingly popular. The protocols include protocols such as 802.11 (as described in the 802.11 wireless standard), home RF, and Bluetooth. The most commercially successful standard wireless protocol to date is the 802.11b protocol.

Although the technical specifications of products using the above-mentioned standard wireless protocols generally indicate a data rate of about 11 MBPS and a range of, for example, about 100 meters, the performance level is rarely achieved. This lack of performance is attributed to the attenuation of the radiation path of the RF signal, which is usually in the range of 2.4 GHz in indoor environments. The base-to-receiver range is usually less than the coverage required in a typical home, and may only be 10 to 15 meters. In addition, in a structure with a layered floor plan, such as a ranch style or two-story room, or a structure made of materials that attenuate RF signals, the area that requires wireless coverage may be physically larger than that based on 802.11 protocol systems. The range of distance isolation. Finally, the data rate of the above standard wireless protocols depends on the signal strength. As the distance within the coverage area increases, wireless system performance usually degrades.

One way to increase the range of a wireless system is to use repeaters. This is a common practice in the mobile wireless industry. A significant problem is that the system receiver and transmitter use the 802.11 or 802.16 WLAN wireless protocol to operate at the same WLAN frequency. This operation is commonly referred to as time division duplexing. The operation is significantly different from many cellular repeater systems, such as systems based on IS-136, IS-95 or IS-2000 standards, in which the receive and transmit bands are separated by a duplex frequency offset. Frequency division duplexing makes repeater operation easier compared to situations where the receiver and transmitter channels are at the same frequency.

However, there are cellular mobile systems that use time instead of frequency to separate the receive and transmit channels. The system uses a predetermined time for specific uplink/downlink transmissions. The repeater of the system is easy to set up because the transmission and reception times are known by the base station and broadcast by the base station. The receiver and transmitter of the system may be isolated in several ways, including physical separation, antenna pattern, or polarization isolation.

The random grouping nature of the WLAN protocol provides undefined reception and transmission periods. Packets from each wireless network node are spontaneously generated and transmitted, and are temporarily unpredictable. A protocol called contention and random compensation protocol is used to prevent two units from transmitting their packets at the same time. For the 802.11 standard protocol, this is called Distributed Coordination Function (DCF).

WLAN repeaters have unique limitations due to the above spontaneous transmission performance, and therefore require unique solutions. Another unique requirement is that since the repeater uses the same frequency for reception and transmission, some form of isolation must exist between the receiver and the transmitter of the receiver. Although existing CDMA systems use directional antennas and physical separation of receiving and transmitting antennas to achieve the isolation, the technology is used in many operating environments, such as homes where laying long cables is not ideal or may be too costly. Not applicable to WLAN repeaters.

Summary of the invention

The wireless repeater of the present invention solves the above-mentioned problems related to spontaneous transmission and transceiver isolation by using a unique frequency detection and conversion method. The wireless repeater enables two WLAN units to communicate by converting the packet from a first frequency channel communication used by one device to a second frequency channel used by a second device. The direction of the transformation from the first frequency channel to the second frequency channel relative to the transformation from the second frequency channel to the first frequency channel depends on the real-time configuration. The repeater monitors the two channels used for transmission, and when a transmission on the channel is detected, switches the received signal to the other channel on which it is transmitted.

Therefore, the wireless repeater of the present invention can realize high-speed communication between the transmitter and the receiver, and the transmitter and the receiver may be isolated from each other in a conventional WLAN environment. In addition, the repeater is small and relatively inexpensive, and responds to the transmission by monitoring and responding, thereby avoiding spontaneous transmission.

Description of the drawings

Fig. 1 is a block diagram of a wireless network including a WLAN repeater according to a preferred embodiment of the present invention.

Fig. 2 is a detailed block diagram of the repeater shown in Fig. 2.

Fig. 3 is a detailed block diagram of an alternative front end of the repeater shown in Fig. 2 using a bi-orthogonal polarized antenna.

Fig. 4 is a detailed block diagram of an alternative front end of the repeater shown in Fig. 2 using bidirectional antennas and switches.

detailed description

1, a wide area connection 101 is connected to a wireless gateway or access point 100. The wide area connection is, for example, an Ethernet connection, a T1 line, a broadband wireless connection, or any other electronic connection that provides data communication. The wireless gateway 100 is based on Bluetooth, Hyperlan or other wireless communication protocols, and transmits RF signals such as IEEE 802.11 packets or signals to client devices 104, 105, such as personal computers, personal digital assistants, or any other wireless protocol that can pass through one of the above wireless protocols. A device that communicates with other similar devices. The individual propagation or RF paths to each of the client devices are shown as 102,103.

Although the signal transmitted via the RF path 102 has sufficient strength to maintain high-speed data packet communication between the client device 104 and the wireless gateway 100, when passing through a structured obstacle such as the wall 106, it is transmitted to it if there is no wireless The repeater 200, if there is a point where few data packets are received in each direction, the signal transmitted via the RF path 103 and intended for use by the client device 105 may be attenuated. The following will describe the wireless The structure and operation of the repeater.

In order to increase the coverage area and/or communicate the data rate to the client device 105, the wireless repeater 200 receives the packet transmitted on the first frequency channel 201 from the wireless gateway 100. For example, a wireless repeater 200 having a size of 2.5"×3.5"×.5" and preferably capable of being inserted into a standard electrical socket and operating at 110V AC power detects the presence of a packet on the first frequency channel 201, Receive the packet and transmit the packet with higher power on the second frequency channel 202. Unlike the conventional WLAN operating protocol, the client device 105 operates on the second frequency channel, but the wireless The gateway 100 operates on the first frequency channel. In order to perform the packet return operation, the wireless repeater 200 detects the presence of the packet transmitted from the client device 105 on the second frequency channel 202, The packet is received on the frequency channel 202, and the packet is transmitted on the first frequency channel 201. Then, the wireless gateway 100 receives the packet on the first frequency channel 201. In this way, the wireless The relay 200 can receive and transmit signals at the same time, and extend the coverage area and performance of the wireless gateway 100 to the client device 105.

It should be understood that the wireless repeater 200 may be used in a similar manner to improve communication from one client device to another client device within a peer-to-peer network. When there are many units isolated from each other, the wireless repeater 200 acts as a wireless hub that allows two groups of different units to communicate, and standard RF propagation and coverage may not enable the units to communicate.

Figure 2 shows the wireless repeater 200 in more detail. The key feature of the wireless repeater 200 is that it can receive a signal and convert the frequency of the received signal from a first two-way frequency to a second two-way frequency, and the signal is only slightly distorted. This is performed through fast signal detection and the delay of the received signal long enough to determine the appropriate control behavior.

The radio waves propagate from various wireless devices such as the client devices 104, 105 of FIG. 1, so that the antenna 300 can obtain the radio waves, which is electromagnetically connected to a voltage sensor, as is well known to those skilled in the art. In a preferred embodiment, this may be tuned and matched to the frequency of interest by a single omnidirectional antenna. Other embodiments may include directional two-dimensional antennas, dual antenna units, polarized antenna units, and directional arrays, but are not limited to these.

The antenna 300 shown in FIG. 2 converts the received radio waves into voltage signals, and feeds the voltage signals to the isolator 305. Alternatively, the isolator may not be included, depending on the type of antenna configuration used. Two such antenna configurations will be described below. The isolator 305 allows signals to be transmitted from the antenna 300 to the low noise amplifier (LNA) 310 and from the power amplifier 325 to the antenna 300, but blocks or isolates the LNA 310 and the power amplifier 325. Other implementations of the isolator 305 may include circulators, directional couplers, splitters, switches, etc., but are not limited thereto. For example, the switch may be used with the bidirectional antenna configuration that will be described in FIG. 4. The signal received and transformed by the antenna 300 passes through the isolator 305 and is fed to the LNA 310, which amplifies the signal and sets the noise level at this time. The signal amplified by the LNA 310 is fed to an RF splitter 315, which performs an RF power splitting or coupling function on the signal to split the signal into two different paths. The splitter 315 may also be a directional coupler, or any device that can divide one signal into two signals.

At this time, those skilled in the art should understand that the antenna 300, the LNA 310, and the RF splitter 315 are the main components forming the receiver in the repeater 200. In addition, those skilled in the art should understand that the antenna 300, the power amplifier 325, the amplifier 330, the filter 335, the switch 345, and the mixer 350 are the main components forming the transmitter in the repeater 200.

The mixers 320 and 321 are frequency conversion devices that mix the signals transmitted from the splitter 315 with the signals output from the local oscillators 340 and 341 at the corresponding frequencies designated as LO1 and LO2 to generate intermediate frequencies (IF) or usually a low frequency signal. The local oscillators 340, 341 are tuned to different frequencies LO1, LO2, so that two different signals of two different frequencies fed from the splitter 315 are transformed into a common IP frequency. For example, if two signals with different frequencies F1=2.412GHz and F2=2.462 are output from the splitter 315 to the mixers 320 and 321, respectively, it is assumed that the mixer 320 is performing low-side mixing. While the mixer 321 is performing the high-side mixing function, the local oscillator 340 is tuned to LO1=2.342GHz, and the local oscillator 341 is tuned to LO2=2.532GHz, and inputs are provided In the case of the mixers 320 and 321, the frequency of each signal output from the mixers 320 and 321 is converted into an IF of 70 MHz.

The splitters 323 and 324 that operate in the same manner as the splitter 315 described above divide the IF signals output from the corresponding mixers 320 and 321 into two different paths. One path from each of the splitters 323, 324 leads to the filters 360, 361, respectively, and the other path from each of the splitters 323, 324 is generally a filter 365, 366.

It is preferable that the filters 360, 361 of the band-pass filter with delay remove all outputs except for the required frequency part from the mixing operation. Preferably, the filters 360 and 361 have a sufficient time delay, so that the detection and control unit 362 can detect two RF signals before obtaining the signal from the output terminals of the filters 360 and 361. Which of the frequencies exists, and performs the control function described below because the detectors 370 and 371 are connected in parallel with the delay filters 360 and 361. Methods of delaying electronic signals are well known to those skilled in the art, including surface acoustic wave (SAW) devices, but are not limited to this. However, if it is acceptable to intercept a part of the first part of the RF signal, the filters 360, 361 will not require a specified delay.

Those skilled in the art should also understand that the mixers 320 and 321, the splitters 323 and 324, and the filters 360 and 361 are the main components forming the frequency converter in the repeater 200.

The filters 365, 366 in the detection and control unit 362 also perform the same type of band-pass filtering as the filters 360, 361. The main difference is that the filters 365, 366 are preferably fast filters without a specified long time delay. In addition, the filters 365 and 366 preferably do not need to have the same level of filtering performance as the filters 360 and 361, but those skilled in the art should understand that changing the filter performance under the limitation of implementing the filtering target is a design choice. Those skilled in the art should also understand that filters or devices other than band-pass filters may be used to perform the above-mentioned band-pass functions.

The power detectors 370, 371 are simple power detection devices that detect whether there is a signal on each of the corresponding frequencies F1, F2, and if the signal exists, provide a proportional voltage output. Many analog detector types that perform this function may be used. For example, the detector includes a diode detector, but is not limited to this. The diode detection may be performed on RF, IF or baseband. It is possible to use detectors that provide higher performance than simple power detectors. It is possible to use SAW equipment to implement the detector as RF or IF matched filtering, and implement baseband matched filtering or correlation after analog-to-digital conversion. The power detectors 370 and 371 are used to determine the existence of wireless transmission on one of the two IF channels by comparing the signals on the two IF channels with a threshold. It is possible to establish a noise level based on monitoring the channel at any time, so as to predetermine or calculate the threshold.

In addition, the power detectors 370, 371 may be used to determine the start and stop time of the detected transmission. As described below, a proportional voltage output by the power detectors 370, 371 in response to signal detection will be used by the microprocessor 385 to control the retransmission of the signal. Those skilled in the art should understand that the power detection can be placed in the signal processing path earlier or later, because the signal can be detected, so that the retransmission process can be turned on or off. In addition, those skilled in the art should understand that techniques for determining or limiting the transmission time can be used, including using a timer to place the time limit on retransmission, but it is not limited to this.

The filters 375 and 376 are low-pass filters, and preferably have a narrower bandwidth than the filters 365 and 366. The filters 375 and 376 are used to delete the remaining high frequency parts after the signal detection by the power detectors 370 and 371, and provide processing gain by reducing the detection signal bandwidth, thereby providing an increase in the signal-to-noise ratio. The signals output from the low-pass filters 375 and 376 are input to the constant-scale digital converters 380 and 381.

After the analog-to-digital converters 380, 381 convert the analog signal representing the detected power of the RF signal into a digital signal in a manner well known to those skilled in the art, the resulting digital signal is sent to the microprocessor 385. The microprocessor 385, which can also be described as a logic state machine, digital signal processor, or other digital processing and control device, can be programmed to implement all necessary control algorithms to detect the presence of F1 or F2 with high probability and certainty, And start the appropriate control function.

Alternatively, it should be noted that a comparison detector (not shown) with adjustable threshold control can be used instead of the analog-to-digital converters 380, 381 and the microprocessor 385. In addition, the control output of the microprocessor 385 may optionally be directly connected to a digital gate to control the exchange, wherein the input to the gate is taken directly from the output of the comparison detector. In addition, the input to the digital logic may come from the microprocessor 385 to allow priority control of the settings provided from the output of the comparison detector. In this case, the microprocessor (385) may continue to control the display function; however, analog signals may be used, and the power detectors 370, 371 may directly control the control of the variable gain amplifier 330.

The feedback to the user can be controlled by the microprocessor 385 via an indicator 390, which is, for example, a series of light emitting diodes, but is not limited to this. The feedback to the user may be an indication that the wireless repeater 200 is in an acceptable position, so that one or two frequencies from the wireless access point 100 and the client device 105 can be detected, or power can be supplied to the wireless repeater 200.

Once any one of the frequencies F1 and F2 is detected, the microprocessor 385 controls the switches 345 and 355. The switch 355 is converted to allow the detected signal at the IF frequency to be routed on F1 or F2 to the input of the frequency converter 350, which is another frequency similar to the mixers 320, 321 Conversion equipment. In addition, the microprocessor 385 sets the switch 345 to allow the signal from the appropriate one of the local oscillators 340, 341 to be routed to the mixer 350, thereby making the input of the frequency converter 350 The IF frequency of the terminal is converted to an appropriate frequency at its output terminal.

The following will describe an example of operating the wireless repeater 200 using the frequency of the previous example: F1=2.412GHz; F2=2.462GhzIF=70MHz; LO1=2.342GHz; and LO2=2.532GHz. Assume that F1 is detected, and the F1 is output from the filter 361. The switch 355 is set to receive its input from the filter 361, the input being F1 converted to 70 MHz. Since F1 needs to be retransmitted at F2=2.462 GHz, the switch 345 is connected to the signal from the local oscillator 341. The output of the frequency converter 350 includes two parts (L21-IF) and (LO2+IF). The required part is LO2-IF, or 2.532GHz-70MHz=2.462GHz. Since the frequency converter 350 generates the sum and difference of the output of the switch 345 and the output of the switch 355, the filter 355 must remove undesirable terms. In the above example, the undesirable term may be LO2+IF or 2.602GHZ.

The filter 335 performs the required filtering operation. If F2 is detected, the same holds true. The sum and difference results will occur, and the filter 335 must filter out undesirable parts. The converted and filtered version of the received signal is applied to the amplifier 330, which is preferably a variable gain amplifier. The amplifier 330 uses a variable gain amount under the control of the microprocessor 385 to ensure that the signal fed to the amplifier 325 is within the target transmission power range. The amplifier 325 is preferably the final power amplifier of the transmission signal. The amplifier 325 feeds its output to the isolator 305, which then sends the signal to the antenna 300. The signal is then converted by the antenna 300 into electromagnetic fields or radio waves in a manner well known to those skilled in the art. The radio wave is a frequency-converted and power-amplified version of the signal received by the antenna 300.

The above description and examples assume frequencies F1 and F2. By moving the frequencies LO1 and LO2 of the local oscillators 340 and 341 to different defined channels and checking the power detection on the channels, it can operate at any frequency F1 and F2. Once the channel is determined, the microprocessor 385 will use the frequency and perform all operations as above. The frequency control of the local oscillators 340 and 341 can be realized by the microprocessor 385 or by user tuning. In the case where the user tunes to control the selected frequency, the repeater may have a set of switches (rotary or other) that may be set by a technician at the time of installation to specify the operating frequency.

Those skilled in the art should understand that the point at which the input signal is frequency-converted from RF to digital signal can be changed, so that more or fewer functions can be performed in the RF domain or the digital domain. In addition, multiple devices such as a wireless gateway (base unit) 100 or client devices 104, 105 can be used in the present invention. The repeater 200 will detect and retransmit signals from any one of the devices. The devices 100, 104, or 105 communicate with each other within the system's protocol (e.g., 802.11), which provides identification of the desired recipient of the retransmitted signal. Therefore, the repeater 100 may serve many host devices.

Referring to Fig. 3, where the same components as those of Fig. 2 are identified by the same reference numbers used in Fig. 2, Fig. 3 shows an alternative embodiment using a bi-orthogonal, or cross, polarized antenna. In this case, two antennas 300b, 300c replace the single antenna 300 and isolator 305 of FIG. 2. In this embodiment, one of the cross-polarized antennas 300b is connected to the power amplifier 355. Another relatively polarized antenna 300c is connected to the LNA 310. The cross-polarized antennas 300b and 300c may be separated or separated by a distance allowed by the assembly of the repeater 200. The quadrature or cross polarization allows the transmitted signal from the PA325 to be isolated from the received signal entering the LNA 310, and can perform a similar function to the isolator 305 of FIG. 2.

Referring to Fig. 4, where the same components as those of Fig. 2 are identified by the same reference numbers used in Fig. 2, Fig. 4 shows an alternative embodiment using a bidirectional antenna. In the described embodiment, two high-gain directional antennas 300d and 300e, and switches 500, 501, and 502 are used to replace the antenna 300 and the isolator 305 in FIG. 2. The embodiment is different from the previously described embodiment in that it allows the repeater 200 to be used in the middle of point-to-point time and benefits from the use of high-gain directional antennas 300d, 300e. For this embodiment, the repeater 200 needs to be able to receive or transmit from each of the two directional antennas 300d, 300e, which is due to the spatial selectivity of each of the antennas.

In this configuration, the switches 500, 501 are nominally set to receive more via the control lines 503, 505, so that the LNAs 310b, 310c are connected to the directional antennas 300d, 300e, respectively. The LNAs 310b and 310c are connected to mixers 320 and 321, respectively. The operation of the detection and IF delay process is the same as that described in conjunction with FIG. 2. Once a signal from an antenna (for example, 300d) is detected, the control lines 503, 505 are set to disconnect from the directional antenna 300e on which the signal does not exist during the transmission period, and connect the antenna 300e Connect to the power amplifier 325. The control lines 503, 504, and 505 are used to set switches 500, 501, and 502, respectively, and are coupled to the microprocessor 385, or other digital control logic as described above.

The present invention has been described in detail above with particular reference to the preferred embodiments. However, it should be understood that changes and modifications can be implemented within the scope and spirit of the present invention.