Abstract: Systematic transmit IQ phase and amplitude imbalances in the transmit chain of a wireless local area network (WLAN) cause a corresponding systematic shift in the roots of a constellation diagram. Additional random phase noise in the transmit chain will cause a further Gaussian distribution of points in the constellation diagram about the systematically shifted roots. This random distribution represents a true error vector magnitude (EVM). By transmitting a known training sequence through the transmit chain, which it is known will be shifted to all of the systematically shifted roots in the constellation diagram, the Gaussian spread around those shifted roots can be analysed to determine the true EVM.

Abstract: A multi-mode access point (AP) and a method of controlling access between that AP and one or more clients is disclosed. In a first time period, the AP commands the client(s) not to send data on a first channel, using, for example, the 802.11a Wireless Local Area Network (WLAN) Standard. The AP is enabled, in that first time period, to receive data on a second channel using say, the 802.11b WLAN standard. At the end of the first time period, the AP switches so that the first channel is commanded to be silent while data can instead be sent via the second channel. Data queuing for a given channel can take place at the or each client when that channel is commanded to be silent, for subsequent transmission when that channel is enabled again.

Abstract: A method of handling data in a wireless LAN comprises contending for control of the medium using a CSMA/CA mechanism or the like. Once control has been established data is sent from the node which has established that control, to a second node. The acknowledgement of receipt issued by that second node in consequence is combined with a payload at that second node and which is intended to be sent to the first node anyway, and a single frame, with the payload piggybacked onto the acknowledgement is returned to the first node. Bidirectional transmission of combined data and acknowledgement continues in a frame bursting manner until a time limit is reached or all data has been transmitted, whereafter contention commences again.

Abstract: A method of synchronizing an Orthogonal Frequency Division Multiplexed (OFDM) IEEE 802.11a data packet at a receiver is disclosed. The 802.11a data packet has a series of short training sequence (STS) symbols as a preamble. Cross-correlation at the receiver of the STS in the 802.11a packet PLCP preamble with the modified reference STS, that is 10 circular shifted by eight samples, results in a main correlation peak but with reduced pre- and post-lobes. To locate the cross-correlation peak, a running second derivative of the cross-correlation function is performed. Peak selection employs a running comparison of the position and magnitude of all peaks in the intermediate neighborhood of the local peaks. Following selection of a peak from within the cross-correlation function of the first STS in the PLOP preamble, both the position and magnitude of the first STS is compared to those of the second STS. Based on the two independent calculations, the start of the OFDM frame is estimated.

Abstract: A method and apparatus for terminating frame reception in a wireless Local Area Network. A node receiving a frame transmitted on the common channel in a wireless Local Area Network determines the destination address of the frame. If the destination address indicates that the transmitted frame is not intended for that node, the node terminates reception of the frame for a time period at least as long as the time required to transmit the remainder of the transmitted frame. In a further embodiment, the time period can also include at least one Short Inter Frame Space and the time required to send an Acknowledgement frame.

Abstract: A method of synchronising an Orthogonal Frequency Division Multiplexed (OFDM) IEEE 802.11a data packet at a receiver is disclosed. The 802.11a data packet has a series of short training sequence (STS) symbols as a preamble. Cross-correlation at the receiver of the STS in the 802.11a packet PLCP preamble with the modified reference STS, that is circular shifted by eight samples, results in a main correlation peak but with reduced pre- and post-lobes. To locate the cross-correlation peak, a running second derivative of the cross-correlation function is performed. Peak selection employs a running comparison of the position and magnitude of all peaks in the intermediate neighbourhood of the local peaks. Following selection of a peak from within the cross-correlation function of the first STS in the PLCP preamble, both the position and magnitude of the first STS is compared to those of the second STS. Based on the two independent calculations, the start of the OFDM frame is estimated.

Abstract: A method of synchronising an Orthogonal Frequency Division Multiplexed (OFDM) IEEE 802.11a data packet at a receiver is disclosed. The 802.11a data packet has a series of short training sequence (STS) symbols as a preamble. Cross-correlation at the receiver of the STS in the 802.11a packet PLCP preamble with the modified reference STS, that is circular shifted by eight samples, results in a main correlation peak but with reduced pre- and post-lobes. To locate the cross-correlation peak, a running second derivative of the cross-correlation function is performed. Peak selection employs a running comparison of the position and magnitude of all peaks in the intermediate neighbourhood of the local peaks. Following selection of a peak from within the cross-correlation function of the first STS in the PLCP preamble, both the position and magnitude of the first STS is compared to those of the second STS. Based on the two independent calculations, the start of the OFDM frame is estimated.

Abstract: An automatic gain control (AGC) circuit has an automatic gain controlled amplifier connected in series with a DC blocking capacitor. A reference DC voltage is selectively applied to an input of the automatic gain controlled amplifier and to an output of the DC blocking capacitor output so as to cause the DC blocking capacitor to store a charge proportional to a DC voltage offset introduced by the controllable gain amplifier. The selectively application of the reference DC voltage is momentarily applied for a duration of less than about 1 microsecond and preferably about 0.4 microseconds. The AGC circuit, including both the amplifier and capacitor, are fabricated as an integrated circuit device.

Abstract: A frequency synthesiser 50 comprises a VCO 56 whose output signal frequency is proportional to input voltage amplitude. In a first mode, the VCO output is fed via a divider 24 to a phase detector 26 which also receives a reference signal. The phase detector output passes via a loop filter 28 and a controller 70, which is passive in the first mode, back to the VCO 56 to form a closed phase-locked loop. To adjust the frequency synthesiser output frequency, the controller 70 switches the circuit into a second mode in which the VCO 56 output is not fed back, and a constant voltage source is supplied to the VCO 56 instead so that the VCO output frequency is constant. The VCO transfer function is then altered by adjusting a variable capacitor 60 therein, and the circuit is then switched back to the first mode. The locking time of the synthesiser is thereby improved as output frequency changes.