Coded data generation or conversion – Digital code to digital code converters
Reexamination Certificate
2003-10-03
2004-12-14
Young, Brian (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
C714S786000, C714S752000
Reexamination Certificate
active
06831574
ABSTRACT:
FIELD OF THE INVENTION
This present invention relates to decoding and more particularly to an efficient scheme for decoding in multiple access communications channels.
BACKGROUND OF THE INVENTION
The explosive growth in the demand for wireless communications has been a phenomenal and worldwide event. There are already over 500 million users that subscribe to cellular telephone services and the number is increasing exponentially. The advantages of wireless tools are obvious, and the number of cellular subscribers will soon exceed the number of fixed line telephone installations. Cellular usage is beginning to become the primary phone option, and as more and more content and wireless tools become available, the increase will continue to expand and proliferate across the globe.
In addition to the explosion of cellular usage, there are other wireless implementations such as Internet access, messaging, paging, wireless local area networks (WLANs). With respect to cellular services, the vast majority of users currently subscribe to digital cellular networks, and the typical state of the art cellular handset is based on digital technology such as GSM, TDMA (IS-136) or CDMA (IS-95), although the legacy analog systems using protocols AMPS and TACS are still in operation.
New, emerging receiver processing procedures allow for huge increases in the utilization of multiple access communications, especially in the wireless sector. The tremendous growth and for wireless cellular phones, wireless personal digital assistants (PDA's), laptops and mobile tablets demonstrates the huge volume of traffic and the varying content desired by the public. There are a number of protocols established to define the bandwidth characteristics, including 3G, IEEE 802.11, and Bluetooth, however the number of users and devices requires more users than available bandwidth. The ability to access data and communicate anywhere at anytime has enormous potential and commercial value.
The content of the wireless sector is also changing, with more and more data being transmitted, including Internet connectivity and live feeds. The usage involving personal digital assistants (PDA's) and even smart appliances have created new markets utilizing wireless data communications. And, this wireless phenomenon is not limited to any geographical boundaries, as the growth is occurring around the globe.
Thus, despite the advancements in wireless transmission and reception, there is a growing problem of extracting more information signals within a limited bandwidth. Emerging multiple-access receiver processing procedures allow for multiple users to access the same communications medium to transmit or receive information. In addition to the problems associated with multiple users in a given bandwidth, an additional problem is the inability to process the data in the receivers in real time. Advanced receiver techniques cover several areas, namely interference suppression (also called multi-user detection), multipath combining and space-time processing, equalization, and channel estimation. These various techniques can be mixed and matched depending upon the circumstances. Proper signal processing of transmitter and receiver yield a far greater potential than current systems.
While the discussion herein illustrates wireless communications, the multiple access topology is equally applicable to wired cable systems and local area networks, read/write operations of a disc drive, satellite communications and any application that benefits from processing of digital data from among many multiple sources. The use of the term ‘users’ is therefore utilized as a convention to describe processing among a plurality of signal sources.
The entire field of digital communications encompasses some sophisticated processing and is deployed in a wide range of applications and electronics. Digital communication techniques are now used for communication of combined audio and video telephony. Communication networking also has exploded as affordable connectivity with greater bandwidth has become available via WiFi, satellite, modulated communications over power lines, cable connections, telephone connections and various hybrid systems.
Regardless of the manner in which the communications are delivered, reliable communications are essential. The quality of the communications depends upon the accuracy with which the transmitted signals match the received signals. While some forms of communications, such as audio, can withstand significant bit loss, digital data communications require greater fidelity in order to be successfully processed. Error control coding is used to provide the required fidelity in the presence of channel noise without increasing the power of the transmitted signal.
Terrestrial and satellite radio systems operate over RF propagation channels that induce signal waveform and spectrum distortions, including signal attenuation and multi-path fading. These applications generally use a Forward error correction (FEC) and are designed according to factors such as modulation formats, error control schemes, demodulation and decoding techniques and hardware components to optimize system performance and implementation complexity. Advanced techniques such as multi-user detection and error correction are also used in applications other than wireless communications and data networking systems. For example, the storage and subsequent retrieval of stored computer data utilizes error correction techniques to ensure exact fidelity of the data. Equipment such as compact disc players, digital audio tape recorders and players also employ error correction techniques to provide high fidelity output. However, for convenience, a further discussion of multiple access wireless communications is included herein to describe processing of data with error corrections.
Existing wireless communication systems generally employ a match between the transmitter encoding and the receiver decoding schemes. The transmitter typically incorporates one or more encoders, one or more interleavers, a symbol generator (i.e. bit to symbol mapper) and modulator. Input data bits to be transmitted are input to the encoder that can encompass one of the various error correction encoders such as Reed Solomon, convolutional encoder, and parity bit generator. The function of each encoder is to add redundancy to enable detection and/or correction of errors in transmission. The output bits from the encoder may then be interleaved wherein the order of the bits is changed to more efficiently combat burst errors. The re-arrangement of the bits caused by interleaving improves the resistance to error bursts while adding latency and delay to the transmission. The first encoder is called the outer encoder and the second encoder is called the inner encoder. The purpose of applying two encoders rather than one (more complex) more powerful code is to reduce the decoding complexity required at the receiver while combating the effects of different types of transmission errors, such as burst errors caused by channel fading as well as random bit errors caused by white noise.
The output bits from the second interleaver are then mapped to symbols by a bit to symbol mapper, wherein the bit to symbol mapper transform the bits to modulator symbols. For example, an 8-PSK (phase-shift keying) modulator uses 8 symbols and the mapper takes three bits and converts them to one of eight symbols. Thus, the bit to symbol mapper generates a symbol for every three input bits in that example.
The output from the symbol mapper is input to a modulator that receives symbols in the M-ary alphabet and generates the analog signal that is subsequently transmitted over the channel by an antenna in wireless applications. The channel may comprise a mobile wireless channel, such as cellular or satellite. There can also be hard wired channel, such as a cable such as Ethernet. The industry strives to employ a transmitter that generates a signal in such a way that it is correctly reconstructed by the receiver.
At the receiver, the
Egnor Dianne E.
MacLeod Robert B.
McElwain Thomas P.
Mills Diane G.
BAE Systems Information and Electronic Systems Integration INC
Maine & Asmus
Nguyen John B
Young Brian
LandOfFree
Multi-turbo multi-user detector does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-turbo multi-user detector, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-turbo multi-user detector will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3334968