Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-09-23
2003-03-25
Ton, Dang (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S465000
Reexamination Certificate
active
06539031
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a wireless network for a metropolitan area. More particularly, the invention relates to adaptive countermeasures for wireless communication of Fast Ethernet data packets in response to environmental and data traffic conditions in an metropolitan area.
BACKGROUND OF THE INVENTION
Computers utilized in modern office environments are typically coupled to a local area network (LAN). The LAN allow users of the computers to share common resources, such as a common printer included in the network, and allows the users to share information files, such as by including one or more file servers in the network. In addition, the users are typically able to communicate information with each other through electronic messaging. A commonly utilized type of LAN is Ethernet. Currently, a variety of products which support Ethernet are commercially available from a variety of sources. Other types of LANs are also utilized, such as token ring, fiber distributed data interface (FDDI) or asynchronous transfer mode (ATM).
LANs are often connected to a wide area network (WAN) via a telephone modem. Thus, information is communicated over the WAN via a communication link provided by a telephone service provider. These telephone links, however, are generally designed to have a bandwidth that is sufficient for voice communication. As such, the rate at which information can be communicated over these telephone links is limited. As computers and computer applications become more sophisticated, however, they tend to generate and process increasingly large amounts of data to be communicated. For example, the communication of computer graphics generally requires a large amount of bandwidth relative to voice communication. Thus, the telephone link can become a data communication bottleneck.
Business organizations and their affiliates are often spread over several sites in a metropolitan or geographical area. For example, a business organization can have a headquarters, one or more branch offices, and various other facilities. For such business organizations, LANs located at the various sites will generally need to communicate information with each other. Wireless communication links for connecting local area networks are known. For example, U.S. Pat. No. 4,876,742, entitled “Apparatus and Method for Providing a Wireless Link Between Two Area Network Systems,” and U.S. Pat. No. 5,436,902, entitled “Ethernet Extender,” each disclose a wireless communication link for connecting LANs.
Availability is a measure of the average number of errors which occur in digitally transmitted data. An availability of 99.99 percent is commonly required for radio communications. For an availability of 99.99 percent, the average error rate for digitally communicated data must be maintained below 1×10
−6
errors per bit, 99.99 percent of the time. The integrity of a wireless communication link, however, is largely dependent upon transient environmental conditions, such as precipitation. Environmental precipitation causes a severe attenuation of the transmitted signal. For example, to maintain an availability of 99.99 in the presence of environmental precipitation, the signal must be transmitted at a level that is 24 dB/km higher than otherwise. Therefore, to ensure an acceptable data error rate under all expected conditions, data is typically communicated over a wireless communication link at a relatively high power and at a relatively low rate. The amount of data required to be communicated over the wireless link, however, can vary widely over time and can vary independently of environmental conditions. In addition, wireless links, especially those operated at high power levels, can cause interference with other wireless links operating in the same geographical area. Thus, the wireless link can become a data communication bottleneck.
Therefore, a technique is needed for efficiently and cost effectively communicating data over a wireless link between Ethernet local area networks.
SUMMARY OF THE INVENTION
The invention is a method and apparatus for implementation of adaptive countermeasures for wireless transmission of Fast Ethernet data packets. A method of communicating between terminals of a wireless link, wherein the method includes steps of receiving Ethernet data packets for communication over a wireless link, formatting the Ethernet data packets according to radio frames, communicating the radio frames over a wireless link, and selectively activating a technique for altering a manner in which the radio frames are communicated over the wireless link. The method can include a step of selectively activating a technique for implementing flow control on the Ethernet data packets. The technique for implementing flow control can include steps of storing the Ethernet data packets in a storage buffer, and removing the Ethernet data packets from the storage buffer prior to performing the step of formatting. The technique for implementing flow control can be performed in response to a pause packet in accordance with IEEE 802.3x.
The technique for altering a manner in which the radio frames are communicated can alter a modulation scheme for transmitting the radio frames, error correction coding for transmitting the radio frames, spectrum spreading for transmitting the radio frames, a power level for transmitting the radio frames or a data transmission rate for transmitting the radio frames. The radio frames can be communicated according to a first transmission rate, where the step of formatting the Ethernet data packets according to radio Frames comprises steps of storing packet data from a complete Ethernet data packet in a packet buffer and retrieving the packet data from the packet buffer only after completion of the step of storing; and wherein when the radio frames are communicated according to a second transmission rate, the step of formatting the Ethernet data packets according to radio frames comprises steps of storing packet data from an Ethernet data packet in a packet buffer and retrieving packet data for the Ethernet data packet while the step of storing the packet data is still being performed. The first transmission rate can be higher than the second transmission rate.
The method can include a step of monitoring a hit error rate associated with the radio frames communicated via the wireless link and wherein the step of selectively activating a technique for altering the manner in which the radio frames are communicated is performed in response to the bit error rate. The step of selectively activating can includes steps of comparing the bit error rate to a first threshold and when the bit error rate exceeds the first threshold, altering a modulation scheme for transmitting the radio frames from a first modulation scheme to a second modulation scheme. The first modulation scheme can be quadrature amplitude modulation (QAM) and the second modulation scheme can be quadrature phase-shift modulation (QPSK). The method can also include steps of comparing the bit error rate to a second threshold lower than the first threshold and when the bit error rate falls below the second threshold, altering the modulation scheme for transmitting the radio frames from the second modulation scheme to the first modulation scheme. The step of selectively activating can include steps of comparing the bit error rate to a first threshold and comparing a rate of change in the bit error rate to a first reference and when the bit error rate exceeds the first threshold and the rate of change in the bit error rate exceeds the first reference, altering a modulation scheme for transmitting the radio frames from a first modulation scheme to a second modulation scheme.
The method can include a step of monitoring a received signal level associated with the radio frames communicated via the wireless link and wherein the step of selectively activating the technique for altering the manner in which the radio frames are communicated is performed in response to the received signal level. The step of selectiv
Denton Darryl
Huen Tat
Nattiv Moshe
Ngoc Tho Le
Treadaway Kirk
Browdy and Neimark , P.L.L.C.
Innowave ECI Wireless Systems Ltd.
Ton Dang
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