Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1999-12-24
2004-07-27
Tu, Christine T. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S755000
Reexamination Certificate
active
06769089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to coding methods and apparatuses, and more particularly to a method and apparatus for concatenated channel coding in a data communication system.
2. Description of Related Art
As described in the commonly assigned related co-pending application Ser. No. 08/974,376, a wireless communication system facilitates two-way communication between a plurality of subscriber radio stations or subscriber units (fixed and portable) and a fixed network infrastructure. Exemplary communication systems include mobile cellular telephone systems, personal communication systems (PCS), and cordless telephones. The key objective of these wireless communication systems is to provide communication channels on demand between the plurality of subscriber units and their respective base stations in order to connect a subscriber unit user with the fixed network infrastructure (usually a wire-line system). In the wireless systems having multiple access schemes a time “frame” is used as the basic information transmission unit. Each frame is sub-divided into a plurality of time slots. Some time slots are used for control purposes and some for information transfer. Subscriber units typically communicate with a selected base station using a “duplexing” scheme thus allowing for the exchange of information in both directions of connection.
Transmissions from the base station to the subscriber unit are commonly referred to as “downlink” transmissions. Transmissions from the subscriber unit to the base station are commonly referred to as “uplink” transmissions. Depending upon the design criteria of a given system, the prior art wireless communication systems have typically used either time division duplexing (TDD) or frequency division duplexing (FDD) methods to facilitate the exchange of information between the base station and the subscriber units. Both the TDD and FDD duplexing schemes are well known in the art.
Recently, wideband or “broadband” wireless communications networks have been proposed for delivery of enhanced broadband services such as voice, data and video. The broadband wireless communication system facilitates two-way communication between a plurality of base stations and a plurality of fixed subscriber stations or Customer Premises Equipment (CPE). One exemplary broadband wireless communication system is described in the co-pending application Ser. No. 08/974,376 which now is a U.S. Pat. No. 6,016,311, and is shown in the block diagram of FIG.
1
. As shown in
FIG. 1
, an exemplary broadband wireless communication system
100
includes a plurality of cells
102
. Each cell
102
contains an associated cell site
104
that primarily includes a base station
106
and an active antenna array
108
. Each cell
102
provides wireless connectivity between the cell's base station
106
and a plurality of customer premises equipment (CPE)
110
positioned at fixed customer sites
112
throughout the coverage area of the cell
102
. The users of the system
100
may include both residential and business customers. Consequently, the users of the system have different and varying usage and bandwidth requirement needs. Each cell may service several hundred or more residential and business CPEs.
The broadband wireless communication system
100
of
FIG. 1
provides true “bandwidth-on-demand” to the plurality of CPEs
110
. CPEs
110
request bandwidth allocations from their respective base stations
106
based upon the type and quality of services requested by the customers served by the CPEs. Different broadband services have different bandwidth and latency requirements. The type and quality of services available to the customers are variable and selectable. The base station media access control (“MAC”) allocates available bandwidth on a physical channel on the uplink and the downlink. Within the uplink and downlink sub-frames, the base station MAC allocates the available bandwidth between the various services depending upon the priorities and rules imposed by their quality of service (“QoS”). The MAC transports data between a MAC “layer” (information higher layers such as TCP/IP) and a “physical layer” (information on the physical channel).
Due to several well known communication phenomenon occurring in the transmission link between the base stations
106
and the CPEs
112
, it is well known that the transmission links or channels may be noisy and thereby produce errors during transmission. These errors are sometimes measured as Bit Error Rates (BERs) that are produced during data transmission. Depending upon the severity of these errors, communication between the base stations
106
and the CPEs
112
can be detrimentally affected. As is well known, by properly encoding data, errors introduced by noisy channels can be reduced to any desired level without sacrificing the rate of information transmission or storage. Since Shannon first demonstrated this concept in his landmark 1948 paper entitled “A Mathematical Theory of Communication”, by C. E. Shannon, published in the Bell System Technical Journal, pps. 379-423 (Part I), 623-656 (Part II), in July 1948, a great deal of effort has been put forth on devising efficient coding and encoding methods for error control in a noisy communication environment. Consequently, use of error correcting coding schemes has become an integral part in the design of modem communication systems.
For example, in order to compensate for the detrimental effects produced by the noisy communication channels (or for noise that may be generated at both the sources and destinations), the data exchanged between the base stations
106
and the CPEs
112
of the system
100
of
FIG. 1
may be coded using conventional combined coding and modulation designs. For example, convolutional or trellis-coded modulation (TCM)-Reed-Solomon (RS) type coders are well known in the art and can be used to code the data as it is exchanged in the system
100
of FIG.
6
. Convolutional or TCM-RS concatenation coding schemes are well known in the communication art as exemplified by their description in the text entitled “Convolutional Coding, Fundamentals and Applications”, by L. H. Charles Lee, published by Artech House, Inc. in 1997, the entire text of which is hereby fully incorporated by reference for its teachings on convolutional/TCM-RS coding schemes and techniques. As is well known, in the past channel coding designs and modulation designs were treated as separate entities. Hamming distance was considered an appropriate measure for system design. TCM design offers the optimum matching between the channel encoder output code vector and the modulator using a special signal mapping technique.
As is well known, the coding gains produced by coding schemes employing convolutional or TCM coding schemes for the inner codes and RS for the outer codes (i.e., concatenating the convolutional/TCM inner codes with the RS outer codes) is relatively high in terms of the minimum Hamming distance and coding rates achieved. Disadvantageously, the high coding gains achieved by these conventional schemes come at a price in terms of complexity, cost, size, speed, data transmission delays and power. As is well known to those of skill in the art, one of the main disadvantages associated with the prior art concatenated coding schemes is that these techniques require the use of symbol “interleavers”. The Convolutional/TCM-RS concatenation techniques must employ a symbol interleaver between the outer and inner codes because when the inner code decoder makes a decoding error, it usually produces a long burst of errors that affect multiple consecutive symbols of the outer decoder. Thus without a deinterleaver, the performance of the outer decoder severely degrades and the effective coding gains produced by the concatenation is lost. Furthermore, the presence of interleaver/deinterleaver distributes the error bursts over multiple outer code words thereby effectively utilizing the power of the outer codes.
In communication systems that transmi
Ensemble Communicatioins, Inc.
Jaquez & Associates
Jaquez, Esq. Martin J.
Tu Christine T.
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