Broadcom Corporation

Lucent Technologies Inc.

Quinn Li

Nallepilli S Ramesh

Steve A Allpress

Stephen Alan Allpress

Xiao Cheng Wu

Raafat Edward Kamel

Carl Francis Weaver

Martin Howard Meyers

Robert Atmaram Soni

Frances Lin Jiang

Alexandro Federico Salvarani

R Michael Buehrer

Sarath Kumar

John Minkoff

An apparatus and method for implementing an equalizer which combines the benefits of a decision feedback equalizer (DFE) with a maximum-a-posterori (MAP) equalizer (or a maximum likelihood sequence estimator, MLSE) to provide an equalization device with significantly lower complexity than a full-state MAP device, but which still provides improved performance over a conventional DFE. The equalizer architecture includes two DFE-like structures, followed by a MAP equalizer. The first DFE forms tentative symbol decisions. The second DFE is used thereafter to truncate the channel response to a desired memory of Lsymbols, which is less than the total delay spread of L symbols of the channel. The MAP equalizer operates over a channel with memory of Lsymbols (where L&#x3c;=L), and therefore the overall complexity of the equalizer is significantly reduced.

High performance equalizer having reduced complexity

An apparatus and method for implementing an equalizer which (1) combines the benefits of a decision feedback equalizer (DFE) with a maximum-a-posterori (MAP) equalizer (or a maximum likelihood sequence estimator, MLSE) (2) performs equalization in a time-forward or time-reversed manner based on the channel being minimum-phase or maximum-phase to provide an equalization device with significantly lower complexity than a full-state MAP device, but which still provides improved performance over a conventional DFE. The equalizer architecture includes two DFE-like structures, followed by a MAP equalizer. The first DFE forms tentative symbol decisions. The second DFE is used thereafter to truncate the channel response to a desired memory of Lsymbols, which is less than the total delay spread of L symbols of the channel. The MAP equalizer operates over a channel with memory of Lsymbols (where L&#x3c;=L), and therefore the overall complexity of the equalizer is significantly reduced.

High performance equalizer with enhanced DFE having reduced complexity

This invention describes an apparatus and method to improve the performance of a decision feedback equalizer (DFE) for time-varying multi-path channels. For minimum-phase channels, the equalization is performed in a time-forward manner. For maximum-phase channels, the equalization is performed in a time-reversed manner. More specifically, for maximum-phase channels, the filter coefficients are computed based on the channel estimates reversed in time, and the filtering and equalization operations are performed with the received block of symbols in a time-reversed order. In the context of this invention, the term 'minimum-phase channel' implies that the energy of the leading part of the channel profile is greater than the energy of the trailing part. The term 'maximum-phase channel' implies that the energy of the leading part of the channel profile is less than the energy of the trailing part.

Decision feedback equalizer for minimum and maximum phase channels

A transmitter for wireless communications provides multiple types of orthogonality to improve transmit diversity. Transmit diversity is improved by using both coding and carrier frequency orthogonality. Data to be transmitted is broken into four parallel channels. Two of the channels are transmitted on a first carrier signal and the other two channels are transmitted on a second carrier signal. Channels transmitted on the same carrier signal are provided with orthogonal codes so that they may be separated by a receiver. Channels transmitted on different carrier signals may be encoded with identical orthogonal codes. The modulated carrier signals are then transmitted using at least two antennas, where one antenna is used for each carrier.

Method of providing downlink transmit diversity

A long code generator is disclosed that maintains a common long code state between a system with multiple spreading rates, such as a spreading rate equal to the chip rate (1&times;) and a spreading rate at a multiple of the chip rate (n&times;), such as three-times the chip rate (3&times;). An n&times; long code generator generates n bits for every clock pulse, where the clock operates at the system chip rate. n bits are generated for every clock period by having the long code mask value assume n values for each clock period. Thus, the long code mask value is changed at n times the chip rate, while the shift register is operated at the chip rate. Each of the long codes corresponding to the n long code mask values are multiplexed, for example, using an interlacing technique. The long code generator includes a conventional shift register, AND gate array, modulo-2 adder and clock. In addition, the disclosed long code generator includes a novel long code mask generator that generates n long code masks for each clock period. The long code mask generator operates with a chip rate of n-times the system clock (n&times;1.2288 MHz). The three long code masks generated for each user must be different from one another, and different from the three long code masks generated for all other users. All the randomness properties necessary for proper CDMA operation are preserved. The present invention applies to both the forward and reverse links for long code generation. Long code state synchronization is maintained between two systems employing different spreading rates, thereby facilitating handoffs without explicit messaging of state information.

Method and apparatus for generation of CDMA long codes

The invention is a method for controlling power on multiple forward link communication channels by using multiple power control sub-channels, wherein each power control sub-channel is associated with a forward link communication channel to be power controlled. A fundamental power control sub-channel and a supplemental power control sub-channel are time multiplexed onto a reverse pilot channel. Transmitted over the fundamental power control sub-channel is a fundamental power control bit for indicating to a base station to increase or decrease its transmission power over a corresponding forward fundamental channel. Transmitted over the supplemental power control sub-channel is a supplemental power control bit for indicating to a base station to increase or decrease its transmission power over a corresponding forward supplemental channel. The pilot sub-channels are preferably separated by the fundamental and supplemental power control sub-channels for time diversity purposes.

Channel structure for forward link power control

A method of controlling the power in a wireless communication system. In one embodiment of the invention, a base station determines the information rate of a signal to be transmitted to a mobile station, and obtains the variable power control scaling factor based on this information rate. The base station then transmits the variable power control scaling factor to the mobile station. The mobile station determines a target signal quality measurement for a received signal from the base station, such as a target E /N , and scales the target E /N by the variable power control scaling factor. The mobile station also obtains an information rate scaling factor based on the information rate of the received signal, and further scales the target E /N by this information rate scaling factor. The mobile station then compares the target E /N to a measured E /N of the received signal. An increase in power of the received signal is requested when the measured E /N of the received signal is smaller than the scaled E /N . A decrease in power of the received signal is requested when the measured E /N of the received signal is larger than the scaled E /N . Providing the variable power control scaling factor to the mobile station allows frames having an information rate lower than the full rate to be transmitted at a power even lower than the power of a frame having an information rate equal to the full rate times the information scaling factor.

Method of power control for a wireless communication system having multiple information rates

In a wireless communications system, a base station transmits power control signals (e.g., the power control bits of a power control sub-channel) to a mobile using a forward-link channel that is decoupled from all other signals transmitted from that base station to that mobile. For example, the decoupled forward-link channel may be a common power control channel. The mobile then uses the power control signals received in the decoupled forward-link channel to control its power level for transmitting one or more reverse-link channels to the base station. The ability of base stations to use decoupled forward-link channels in order to transmit their power control signals to a mobile enables a mobile to operate with different active sets for the forward and reverse links. This enables forward-link data traffic to be implemented using a simplex mode, even when the mobile is operating in soft handoff in the reverse link. This in turn greatly reduces the reactivation time involved in transitioning a mobile from the suspended state to the active state, which is particularly desirable for bursty (i.e., intermittent) packet data flow, as opposed to continuous circuit-oriented voice messaging.

Using decoupled power control sub-channel to control reverse-link channel power

Disclosed is a common transmitter architecture having incorporated both open loop transmit diversity schemes using a plurality of binary switches. Employment of binary switches allows for the sharing of certain components whether the transmitter is utilizing a orthogonal transmit diversity (OTD) scheme or a space time spreading (STS) scheme. Accordingly, the number of components in the transmitter is minimized and the complexity of the transmitter is simple enough to be implemented into a single application specific integrated chip.

Transmitter architecture employing space time spreading and orthogonal transmit diversity techniques

A complex spreading and/or scrambling code sequence generation system uses a first complex code sequence having at least two components and a second complex code sequence having at least two components. The components of the first complex code sequence are respectively mixed with the corresponding components of the second complex code sequence to generate the complex scrambling code sequence. In doing so, an offset between the components of the complex scrambling code sequence is achieved for the same and/or different users. The complex scrambling code sequence can be used for spreading, scrambling, de-spreading or descrambling an information signal.

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Madison, NJ, United States of America

Quinn Li