Field of the Invention

The technical field relates to radio communications, and in particular, to improving performance using diversity transmission.

Background of the Invention

Transmit diversity antennas are used to enhance performance including system capacity and data throughput. With transmit diversity, the required transmit signal power to provide a particular data rate or a particular signal quality can be reduced. Transmit diversity involves transmitting data on two or more antennas, where the geographical separation between the antennas leads to path loss characteristics that are independent from antenna to antenna. However, the signal transmitted from the multiple antennas can combine constructively or destructively over the air at a receiving station, and the receiving station cannot coherently combine signals from the transmit diversity antennas. To alleviate this problem, different signals representing the same data may be transmitted from the two transmit antennas.

One approach for diversity transmission for mobile terminals might be to switch between two or more transmit antennas (“antenna hopping”) on a fixed schedule. Such antenna hopping avoids the likelihood of bad fades in a statistical fashion, i.e., the probability of a bad fade affecting both (all) of the spatially-separated antennas is low. But lacking knowledge of the uplink transmission channel conditions, this kind of fixed schedule antenna hopping has limited promise. In other words, the selected antenna may not be the best antenna for the current channel conditions.

In another approach referred to as delay diversity, the signal transmitted from a second antenna is delayed with respect to the signal transmitted from a first antenna. At the receiver, the resulting signal appears as if it passed through a channel with dispersion, and a well-designed equalizer may be used to achieve performance gain over transmission from a single antenna.

Using two or more antennas to transmit from the mobile station on the uplink to the base station to improve performance introduces additional cost and power concerns. Thus, it is in the art demonstrated that two or more antennas to transmit have great potentials in providing performance but have significant challenges regarding cost, power, size, and interference exist in implementing multiple-antenna transmitter systems.

Thus, therefore there is a need for a method and system for generating a plurality of output sequences from an input sequence to attain an artificial diversity in a wireless communication system, to overcome the above mentioned limitations.

Summary of the Invention

The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

In accordance with one aspect of the present invention is a method for generating a plurality of output sequences from an input sequence to attain an artificial diversity in a wireless communication system, the method comprising: obtaining a first data packet in order to transmit the same to a remote wireless device using a transmission channel, applying a predetermined or random delay value to the imitative first data packet to get a second data packet, performing packet random amplification and phase shifting of the delayed fed second data packet for each of the transmit chains and combining the second data packet with the next arrived data packet in order to transmit the same to a remote wireless device in order to attain the artificial diversity.

Alternative of data packets, the method may be applied to one or more symbols, one or more bit or a fraction of symbol or bit thereof. The combining includes combining the fed one or more symbols, one or more bits or a fraction of symbol or bit thereof with next arrived one or more symbols, one or more bits or a fraction of symbol or bit thereof. The random value of delay or amplification or phase is picked from a set of random numbers having a specified probability distribution function.

The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.

Before undertaking the detailed description of the invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

Brief description of the drawings

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like numbers designate like objects, and in which:

Figure 1 is a typical diagram illustrating a technique for a general multiple antennas system.

Figure 2 shows a technique to attain an artificial diversity in a wireless communication system using a single antenna according to one embodiment of the present invention.

Figure 3 shows a flow chart of a method for generating a plurality of output sequences from an input sequence to attain an artificial diversity in a wireless communication system according to one embodiment of the present invention.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

Detail description of the Invention

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

Figs. 1 through 2, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.

When referred to hereafter, the terminology “wireless transmit/receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to an eNodeB, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment.

Figure 1 is a typical diagram illustrating a technique for a general multiple antenna system. As illustrated in FIG. 1, the source data is first encoded by a MIMO channel encoder (not shown in figure), which has a general structure and could possibly be a concatenation of a channel code and a MIMO signaling scheme, such as space-time code, spatial multiplexing, or beam-forming. Initially a first transmitter is used for transmitting the source data to a remote location (e.g. receiver as shown in figure). The same source data is fed to a delay unit and then transmitted via a second transmitter to the remote location. There may be multiple path with the delay unit is used for transmitting the source data using many number of transmitters for diverse reception. At the receiving station, all signals transmitted from the two or more different antennas are received by two or more receiving antennas.

Figure 2 shows a technique to attain an artificial diversity in a wireless communication system using a single antenna according to one embodiment of the present invention. The source data is first encoded by a channel encoder (not shown in figure). The output from the encoder is transmitted using a transmitter to a remote location for reception. The same output is fed to the delay unit and further multiplied by a pseudo-random complex number such that each output signal has its own randomized amplitude and phase generated by multiplying the encoded signal with the corresponding randomizing coefficients before being transmitted. The resulting output signals are fed into the transmitter for transmitting using the same antenna. Due to the presence of the randomizing coefficients, the effective channel coefficient will be the actual channel coefficient multiplied by the corresponding randomizing coefficients. Since the randomizing channel coefficients change faster than the channel characteristic of the radio channel does, an artificial fast fading channel is obtained. Any type of modulation scheme like PSK, QAM or OFDM may be used as long as the modulated signal is multiplied by a pseudo-random complex scalar before being transmitted. The channel coefficients are complex values and pseudo-randomly selected at each transmission time. The delay unit may also select random value of time for the signal to be delayed.

The output power at each transmission using a single antenna may change at each transmission time. The phase of each complex channel randomizing coefficients will change the phase of the output signal at each transmission, while the magnitude of each complex channel randomizing coefficient will change the output power for each antenna at each transmission time.

As described above, each of the actual channel coefficients is multiplied by the corresponding channel randomizing coefficients to form an equivalent time-varying fast fading channel. This method can be used in different channel scenarios regardless of whether each channel is known, unknown, or partially known.

Embodiments described herein can be applied to systems using Orthogonal Frequency-Division Multiplexing (OFDM). OFDM is a digital multi-carrier modulation scheme, which uses a large number of closely-spaced orthogonal subcarriers. Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-user version of the popular OFDM digital modulation scheme.

Figure 3 shows a flow chart of a method for generating a plurality of output sequences from an input sequence to attain an artificial diversity in a wireless communication system. At step 310, the method obtains a first data packet in order to transmit the same to a remote wireless device using a transmission channel. At step 320, the method further, applies a predetermined delay value to the imitative first data packet to get a second data packet. At step 330, the method performs packet amplification and phase shifting of the delayed fed second data packet for each of the transmit chains. The performing packet amplification and phase shifting are independent and randomly distributed. The packet amplification and phase shifting is performed by multiplying the transmitted data packet with a complex number. Lastly, at step 340, the method combines the second data packet with the next arrived data packet in order to transmit the same to a remote wireless device in order to attain the artificial diversity.

The first packet data and the combined second data packet with the next arrived data packet are transmitted using single antenna. Combining data packet is transmitted via a second transmission channel, where the first transmission channel and the second transmission channel are highly correlated channel or not time-dispersive.

Expressions such as "including", "comprising", "incorporating", "consisting of, "have", "is" used to describe and claim the present invention are intended to be construed in a nonexclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural and vice versa.

FIGS. 1-3are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated, while others may be minimized. FIGS. 1-3 illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.

We Claim:

1. A method for generating a plurality of output sequences from an input sequence to attain an artificial diversity in a wireless communication system, the method comprising:

obtaining a first data packet in order to transmit the same to a remote wireless device using a transmission channel;

applying a delay value to the imitative first data packet to get a second data packet;

performing packet amplification and phase shifting of the delayed fed second data packet for each of the transmit chains; and

combining the second data packet with the next arrived data packet in order to transmit the same to a remote wireless device in order to attain the artificial diversity.

2. The method of claim 1, wherein the first packet data and the combined second data packet with the next arrived data packet are transmitted using single antenna.

3. The method of claim 1, wherein the performing packet amplification and phase shifting are independent and randomly distributed.

4. The method of claim 1, wherein the combined data packet is transmitted via a second transmission channel.

5. The method of claim 1 and 4, wherein the first transmission channel and the second transmission channel are highly correlated channel or not time-dispersive.

6. The method of claim 1, wherein the step of performing packet amplification and phase shifting is by multiplying the transmitted data packet with a complex number.

7. The method of claim 1, wherein the delay value is random.

8. The method of claim 1, wherein the step of combining be at one or more symbols, one or more bits or fraction of symbol or bit or a combination thereof.

9. The method of claim 1, wherein the step of combining includes combining the fed one or more symbols, one or more bits or a fraction of symbol or bit thereof with next arrived one or more symbols, one or more bits or a fraction of symbol or bit thereof.

10. The method of claim 1, wherein the random values of delay, amplification, and phase can be selected based on channel quality.