Method, apparatus and system of multiple-input-multiple-output wireless communication

BACKGROUND OF THE INVENTION

0001A Multiple-Input-Multiple-Output (MIMO) Space-Time-Coding (STC) wireless communication device may implement STC to multiplex data into a plurality of parallel data sequences. The STC device may also include a Space-Time (ST) encoder to encode the data sequences, and a ST decoder to decode received data. The encoded data sequences may be simultaneously transmitted by a plurality of antennas using one frequency channel.

0002A MIMO Multi-Channel (MC) wireless communication device may include a plurality of channel controllers associated with a plurality of Single-Input-Single-Output (SISO) encoders and a plurality of SISO decoders, respectively. Each of the channel controllers may be assigned to a different frequency channel. The MC device may simultaneously transmit and/or receive data over a plurality of different frequency channels.

BRIEF DESCRIPTION OF THE DRAWINGS

0003The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanied drawings in which:

0004<figref idref="DRAWINGS">FIG. 1</figref> is a schematic diagram of a wireless communication system in accordance with some exemplary embodiments of the present invention;.

0005<figref idref="DRAWINGS">FIG. 2</figref> is a schematic illustration of a dual-channel wireless device in accordance with some exemplary embodiments of the invention; and

0006<figref idref="DRAWINGS">FIG. 3</figref> is a schematic illustration of a flow chart of a method of controllably selecting between a spatial-multiplexing modulation method and a frequency-multiplexing modulation method in accordance with some exemplary embodiments of the invention.

0007It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity or several physical components included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. Moreover, some of the blocks depicted in the drawings may be combined into a single function.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

0008In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits may not have been described in detail so as not to obscure the present invention.

0009Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities within the computing system's registers and/or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices. In addition, the term “plurality” may be used throughout the specification to describe two or more components, devices, elements, parameters and the like.

0010Not withstanding any conventional meaning of the term “modem” (e.g., modulator-demodulator), in this application, unless specifically stated otherwise, the term “modem” may refer to a modulator, e.g., a device able to modulate data frames of signals to be transmitted and/or to a demodulator, e.g., a device able to demodulate data frames of received signals, and/or to a device able to both modulate and demodulate signals. Implementations of modems in accordance with embodiments of the invention may depend on specific applications and design requirements. Furthermore, modems in accordance with some embodiments of the invention may be implemented by separate modulator and demodulator units or in a single modulator/demodulator unit, and such units may be implemented using any suitable combination of hardware and/or software.

0011It should be understood that the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the circuits and techniques disclosed herein may be used in many apparatuses such as units of a wireless communication system, such as for example, a Wireless Local Area Network (WLAN) communication system and/or in any other unit and/or device. Units of a WLAN communication system intended to be included within the scope of the present invention include, by way of example only, modems, Mobile Units (MU), Access Points (AP), wireless transmitters/receivers, and the like.

0012Types of WLAN communication systems intended to be within the scope of the present invention include, although are not limited to, “IEEE-Std 802.11, 1999 Edition (ISO/IEC 8802-11: 1999)” standard (“the 802.11 standard”), and more particularly in “IEEE-Std 802.11a-1999 Supplement to 802.11-1999: Wireless LAN MAC and PHY specifications: Higher speed Physical Layer (PHY) extensions in the 5 GHz band”, “IEEE-Std 802.11b-1999 Supplement to 802.11-1999, Wireless LAN MAC and PHY specifications: Higher speed Physical Layer (PHY) extension in the 2.4 GHz band”, “IEEE-Std 802.11g -2003 Supplement to 802.11-1999, Wireless LAN MAC and PHY specifications: Further Higher Data Rate Extension in the 2.4 GHz band, Draft 8.2”, and “IEEE-Std 802.11k-2003 Supplement to 802.11-1999: Wireless LAN MAC and PHY specifications: Specification for Radio Resource Measurement, Draft 0.1”, and the like.

0013Although the scope of the present invention is not limited in this respect, the circuits and techniques disclosed herein may also be used in units of wireless communication systems, digital communication systems, satellite communication systems and the like.

0014Devices, systems and methods incorporating aspects of embodiments of the invention are also suitable for computer communication network applications, for example, intranet and Internet applications. Embodiments of the invention may be implemented in conjunction with hardware and/or software adapted to interact with a computer communication network, for example, a LAN, wide area network (WAN), or a global communication network, for example, the Internet.

0015Reference is made to <figref idref="DRAWINGS">FIG. 1</figref>, which schematically illustrates a wireless communication system <b>100</b> in accordance with an embodiment of the present invention. It will be appreciated by those skilled in the art that the simplified components schematically illustrated in <figref idref="DRAWINGS">FIG. 1</figref> are intended for demonstration purposes only, and that other components may be required for operation of the wireless systems, devices and methods described herein. Those of skill in the art will further note that the connection between components in the wireless devices described herein need not necessarily be as depicted in the schematic diagram of <figref idref="DRAWINGS">FIG. 1</figref>.

0016Communication system <b>100</b> may include wireless communication devices <b>130</b> and <b>110</b>, which may communicate via a wireless link or channel <b>120</b> of wireless communication system <b>100</b>. Although the scope of the present invention is not limited in this respect, communication devices <b>130</b> and <b>110</b> may include wireless modems of computers, and communication channel <b>120</b> may be part of a WAN or a LAN. For example, system <b>100</b> may be a WLAN system, a Wireless Personal Area Network (WPAN), or a Wireless Wide Area Network (WWAN).

0017Although the scope of the present invention is not limited in this respect, the exemplary communication system shown in <figref idref="DRAWINGS">FIG. 1</figref> may be part of a wireless communication system, in which wireless device <b>130</b> is a remote unit (RU) and wireless unit <b>110</b> is an access point (AP). It will be recognized, however, that in some embodiments of the invention either or both communication devices <b>130</b> and <b>110</b> may be mobile stations, a personal digital assistant (PDA) and a server, respectively, access points, base stations, or any other device or combination of devices suitable for communicating within communication system <b>100</b>.

0018Communication device <b>110</b> may include a transceiver <b>102</b>, which may include a transmitter and/or a receiver in any suitable configuration. Transceiver <b>102</b> may include any suitable transmission and/or reception circuitry known in the art for receiving data transmitted, e.g., by device <b>130</b> and/or for transmitting data, e.g., to device <b>130</b>, as described below. Transceiver <b>102</b> may be implemented, for example, in the form of a single unit or in the form of separate transmitter and receiver units using any suitable combination of hardware and/or software as is known in the art. For example, in the context of the embodiment described with reference to <figref idref="DRAWINGS">FIG. 1</figref>, transceiver unit <b>102</b> may operate to both transmit and receive signals.

0019Communication devices <b>130</b> and <b>110</b> may include one or more radio frequency antennas, as is known in the art. For example, device <b>110</b> may include an antenna <b>104</b> associated with transceiver <b>102</b>, and device <b>130</b> may include a plurality of antennas, for example, antennas <b>112</b>, <b>114</b>, and <b>116</b>. Although the scope of the present invention is not limited in this respect, types of antennae that may be used for antenna <b>104</b>, antenna <b>112</b>, antenna <b>114</b>, and/or antenna <b>116</b> may include but are not limited to internal antenna, dipole antenna, omni-directional antenna, a monopole antenna, an end fed antenna, a circularly polarized antenna, a micro-strip antenna, a diversity antenna and the like.

0020Wireless device <b>110</b> may include a processor <b>106</b>, which may be associated with a memory (not shown). Processor <b>106</b> may process data packets of signals received by transceiver <b>102</b> and/or data packets of signals intended for transmission by transceiver <b>102</b>. Wireless device <b>130</b> may include a processor <b>119</b> associated with a memory (not shown), and a controller <b>118</b>. Controller <b>118</b> may be able to control the flow of data to/from processor <b>119</b> and to selectively provide to either a frequency-multiplexing modem <b>138</b> or a spatial-multiplexing modem <b>132</b> a data frame to be transmitted, as described in detail below.

0021According to exemplary embodiments of the invention, modem <b>138</b> may be able to modulate data to be transmitted and/or demodulate received data based on a Multiple-Input-Multiple-Output (MIMO) frequency multiplexing method, i.e., a MIMO multiplexing method using in parallel a plurality of channels separated in frequency, as is known in the art. For example, modem <b>138</b> may implement a MIMO Multi-channel (MC) multiplexing method, as is known in the art.

0022According to exemplary embodiments of the invention, modem <b>132</b> may be able to modulate data to be transmitted and/or to demodulate received data based on a MIMO spatial-multiplexing method, i.e., a MIMO multiplexing method simultaneously using a plurality of spatial channels of one frequency, as is known in the art. For example, modem <b>132</b> may implement a Space-Tine Coding (STC) algorithm, a Space Division Multiplexing (SDM) method, or any other spatial-multiplexing method, as are known in the art.

0023According to exemplary embodiments of the invention, wireless device <b>100</b> may also include a plurality of Radio Frequency (RF) paths <b>134</b> associated with modem <b>138</b> and modem <b>132</b>. Paths <b>134</b> may be adapted to transmit and receive data via antennas <b>112</b>, <b>114</b>, and <b>116</b>, as is known in the art.

0024According to exemplary embodiments of the invention, controller <b>118</b> may selectively transfer data to be transmitted, e.g., provided by processor <b>119</b>, either to modem <b>138</b> or to modem <b>132</b>, based on a predetermined criterion, as described below. The data may be modulated by the selected modem, and transferred via one or more of paths <b>134</b> to an antenna selector <b>136</b>. Modem <b>130</b> may also control antenna selector <b>136</b> to select one or more of antennas <b>112</b>, <b>114</b> and <b>116</b>, e.g., according to one or more frequency channels implemented by the frequency-multiplexing method, e.g., as is known in the art. Data received from one or more of channels <b>134</b>, e.g., via one or more of antennas <b>112</b>, <b>114</b>, and <b>116</b>, may be demodulated by either modem <b>138</b> or modem <b>132</b>. For example, data previously modulated according to the STC method may be demodulated by modem <b>132</b>, and data previously modulated according to the MC method may be demodulated by modem <b>138</b>, e.g., as described below. The demodulated data may be transferred by controller <b>118</b> to processor <b>119</b>, e.g., as described below.

0025It will be noted that wireless device <b>130</b> may be implemented by different architectures, as are known in the art. For example, one or more elements of device <b>130</b>, e.g., processor <b>119</b>, controller <b>118</b>, modem <b>132</b>, modem <b>138</b>, paths <b>134</b> and/or antenna selector <b>136</b>, may be implemented using any suitable combination of hardware and/or software, and may include any circuit, circuitry, unit or combination of integrated and/or separate units or circuits, as are known in the art, to perform desired functionalities. It is noted that the terms “circuit” and “circuitry” as used herein, may include any suitable combination of hardware components and/or software components, e.g., as described below.

0026Reference is made to <figref idref="DRAWINGS">FIG. 2</figref>, which schematically illustrates a dual-channel wireless device <b>200</b> in accordance with some exemplary embodiments of the invention.

0027According to some exemplary embodiments of the invention, device <b>200</b> may be capable of receiving and/or transmitting data using either a STC modem or a dual-channel modem, as described below.

0028According too exemplary embodiments of the invention, device <b>200</b> may include a processor <b>205</b> associated with a controller <b>210</b>, as described in detail below. Device <b>200</b> may also include a dual channel modem <b>220</b> and a STC modem <b>230</b> associated with controller <b>210</b>, respectively, as described below. Device <b>200</b> may also include a first RF path <b>240</b> and a second RF path <b>250</b>, each associated with modem <b>220</b> and modem <b>230</b>. Path <b>240</b> and path <b>250</b> may transmit and/or receive data to/from a plurality of antennas, e.g., antennas <b>290</b>, <b>292</b> and <b>294</b>, via an antenna selection module <b>280</b>, as is known in the art. Path <b>240</b> and path <b>250</b> may include any suitable RF path for transmitting and/or receiving data through a channel, as is known in the art. For example, path <b>240</b> may include a transmission (Tx) sub-module <b>242</b> and a Receiving (Rx) sub-module <b>244</b>, and path <b>250</b> may include a Tx sub-module <b>252</b> and a Rx sub-module <b>254</b>, as are known in the art.

0029According to exemplary embodiments of the invention, modem <b>220</b> may include any suitable dual-channel modem for modulating data to be transmitted and/or demodulating received data according to a MC multiplexing method. For example, modem <b>220</b> may include a channel selection module <b>222</b>, e.g., as is known in the art, to select a frequency channel for transmitting data provided from controller <b>210</b>. For example, the frequency channel may be selected based on a physical-carrier sensing mechanism or a virtual-carrier sensing mechanism, as are defined by the 802.11 standard.

0030Module <b>222</b> may transfer the data from controller <b>210</b> to a first MC-based channel access control module <b>224</b> or to a second MC-based channel access control module <b>226</b>, e.g., based on the selected frequency channel. Each of modules <b>224</b> and <b>226</b> may be adapted to control transmission of the data via an individual frequency channel, e.g., using one or more of antennas <b>290</b>, <b>292</b> and <b>294</b>, as is known in the art.

0031Module <b>222</b> may also be adapted to control antenna selection module <b>280</b> according to one or more frequency channels implemented by the MC multiplexing method, as is known in the art. For example, module <b>222</b> may control selector <b>280</b> to assign one or more of antennas <b>290</b>, <b>292</b> and <b>294</b> for receiving data, e.g., via path <b>240</b>, and to assign one or more of antennas <b>290</b>, <b>292</b> and <b>294</b> for transmitting data, e.g., via path <b>250</b>.

0032Module <b>224</b> may be associated with a first Single-Input-Single-Output (SISO) encoding module <b>228</b> and a first SISO decoding module <b>229</b>, and module <b>226</b> may be associated with a second SISO encoding module <b>225</b> and a second SISO decoding module <b>227</b>. Modules <b>228</b> and <b>225</b> may include any suitable SISO encoding modules, e.g., as are known in the art, adapted to encode the data to be transmitted via paths <b>240</b> and <b>250</b>, respectively. Modules <b>229</b> and <b>227</b> may include any suitable SISO decoding modules, e.g., as are known in the art, adapted to decode data received via paths <b>240</b> and <b>250</b>, respectively. Path <b>240</b> and/or path <b>250</b> may be assigned individually to a channel, e.g., by module <b>224</b> and/or module <b>226</b>, such that a data-frame may be transmitted through one of paths <b>240</b> and <b>250</b>. At least some of antennas <b>290</b>, <b>292</b> and <b>294</b> may be controllably assigned, e.g., by module <b>222</b>, to path <b>240</b> or path <b>250</b>. Thus, modem <b>220</b> may be implemented, for example, to transmit and/or receive data over two frequency channels in parallel, e.g., in full duplex. Module <b>224</b> and module <b>226</b> may also be adapted to check for an acknowledgment (ACK) frame corresponding to the data-frame transmitted, and transfer to module <b>222</b> a signal corresponding to whether an ACK frame was received or not, as is known in the art. Module <b>224</b> and module <b>226</b> may also be adapted to send an ACK frame corresponding to each data-frame received without errors, as is known in the art.

0033According to exemplary embodiments of the invention, modem <b>230</b> may include any suitable modem for modulating data to be transmitted and/or demodulating received data according to a STC multiplexing method. For example, modem <b>230</b> may include a STC-based channel access control module <b>232</b> adapted to control simultaneous transmission via paths <b>240</b> and <b>250</b> of the data received from controller <b>210</b>, e.g., using one frequency channel, as is known in the art.

0034Module <b>232</b> may also be capable of multiplexing the data to be transmitted, e.g., to provide two parallel sequences to be simultaneously transmitted via paths <b>240</b> and <b>250</b>, respectively. Module <b>232</b> may be associated with a MIMO encoding module <b>236</b> and a MIMO decoding module <b>234</b>. Module <b>236</b> may include any suitable MIMO encoding module, e.g., as is known in the art, adapted to encode the two data sequences provided from module <b>232</b>. Module <b>234</b> may include any suitable MIMO decoding module, e.g., as is known in the art, adapted to decode data received simultaneously via paths <b>240</b> and <b>250</b>. Module <b>232</b> may also be capable of demultiplexing decoded data provided from module <b>234</b>, as is known in the art. Thus, modem <b>230</b> may be implemented to transmit or receive a data-frame via one channel on both path <b>240</b> and path <b>250</b> simultaneously.

0035Module <b>232</b> may also be adapted to check if an ACK frame, corresponding to the data-frame transmitted, is received, as is known in the art. Module <b>232</b> may also be adapted to send an ACK frame corresponding to each data-frame correctly received, as is known in the art.

0036According to exemplary embodiments of the invention, controller <b>210</b> may include a selection module <b>211</b> to select between either frequency-multiplexing modulation method, which may be implemented using modem <b>220</b>, or spatial-multiplexing modulation method, which may be may be implemented by modem <b>230</b>, based on the predetermined criterion, as described in detail below.

0037According to exemplary embodiments of the invention, controller <b>210</b> may also include a Tx frame queue module <b>212</b> able to buffer data provided from processor <b>205</b>, as is known in the art. Controller <b>210</b> may also include a Tx control module <b>213</b> associated with queue module <b>212</b> and selection module <b>211</b>. Queue module <b>212</b> may provide Module <b>213</b> with a data-frame, e.g., when a channel is available for transmission. Module <b>213</b> may selectively transfer the data-frame to either module <b>222</b> or module <b>232</b>, in accordance with the modulation method selected by module <b>211</b>. If, for example, the frequency-multiplexing modulation method is selected by module <b>211</b>, module <b>213</b> may transfer the data-frame to module <b>222</b>. Conversely, if the spatial-multiplexing modulation method is selected by module <b>211</b>, module <b>213</b> may transfer the data-frame to module <b>232</b>. Module <b>222</b> or module <b>232</b> may provide Tx control module <b>213</b> with a signal corresponding to whether an ACK frame corresponding to a transmitted data frame was received. If an ACK frame was not received, Tx control module may be able to re-send the data-frame through a different channel, as is known in the art.

0038According to exemplary embodiments of the invention, controller <b>210</b> may also include an Rx flow control module <b>214</b> to transfer demodulated data provided from module <b>226</b>, module <b>232</b> and/or module <b>224</b> to a Rx frame queue module <b>215</b>, as is known in the art. Module <b>215</b> may be able to buffer the data provided from module <b>214</b> and to transfer the buffered data to processor <b>205</b>, as is known in the art.

0039According to some exemplary embodiments of the invention, it may be required to provide device <b>200</b> with information identifying the modulation method, e.g., the frequency-multiplexing modulation method or the spatial-multiplexing method, used for modulating a data-frame to be received by device <b>200</b>. This may be performed, for example, by transmitting to device <b>200</b>, e.g., before switching between multiplexing methods, a training sequence including information corresponding to the selected multiplexing method.

0040According to other embodiments of the invention, it may not be required to inform device <b>200</b> of the multiplexing method used for modulating the data. In such other embodiments, device <b>200</b> may be adapted to detect the multiplexing method used to modulate the received data. For example, modules <b>229</b> and <b>227</b> may be capable of decoding only data-frames previously encoded according to the MC multiplexing method, and module <b>234</b> may be capable to decode only data-frames previously encoded according to the STC multiplexing method.

0041Although the above discussion refers to a dual-channel wireless communication device, e.g., device <b>200</b>, it will be appreciated by those skilled in the art that device <b>200</b> may be modified to implement a communication device of n channels, for example, by replacing paths <b>240</b> and <b>250</b> with n RF paths, by modifying modem <b>230</b> to implement an n-channel STC-based multiplexing method, and by replacing modem <b>220</b> with a suitable n-channel modem, e.g., including n MC channel access control modules, n SISO encoding modules and n SISO decoding modules.

0042According to some embodiments of the invention, module <b>211</b> may select either the frequency-multiplexing modulation method or the spatial-multiplexing modulation method based on a channel quality value. For example, the channel quality may be evaluated based on data provided to module <b>211</b> from module <b>214</b> and/or module <b>213</b>, as described below.

0043According to some exemplary embodiments of the invention, the channel quality may be evaluated in relation to the number of data-frames that are transmitted by device <b>200</b> compared to the number of such data-frames that are acknowledged by, for example, an ACK frame, as described above. The channel quality value may be expressed in terms of a percentage, for example, a Packet Error Rate (PER) percentage, which may be, for example, the number of data-frames for which an ACK frame has not been received, over the number of data-frames transmitted in a particular period. In some embodiments, a success/fail rate of transmitted data-frames may be measured or calculated over an interval of, for example, a most recent group of data-frames that were transmitted, for example, the last 100 or 1000 data-frames transmitted, if desired. In other embodiments, a success/fail rate or a PER may be calculated over a given time period. Thus, for example, module <b>211</b> may evaluate the channel quality based on the PER percentage, e.g., related to previously transmitted data-frames. Other measures or periods of calculations may be used.

0044According to some embodiments of the invention, the channel quality may be expressed in terms of Cyclic Redundancy Check (CRC) error percentage, which may be, for example, the number of data-frames received, e.g., by module <b>214</b>, with an incorrect CRC, over the number of data-frames received in a particular period. Thus, for example, module <b>211</b> may evaluate the channel quality based on the CRC error percentage, e.g., related to previously received data-frames.

0045According to some exemplary embodiments of the invention, one or more frames received by module <b>214</b> may include quality related information, e.g., as defined by the 802.11k standard. For example, if open loop signaling is implemented, e.g., as defined by the 802.11k standard, the quality related information may be part of a preamble of a received data-frame. Additionally or alternatively, for example, if closed loop signaling is implemented, e.g., as defined by the 802.11k standard, the quality related information may be part of a received management frame.

0046According to other exemplary embodiments of the invention, a predetermined training sequence may be received by device <b>200</b>, e.g., at a predetermined time interval, as is known in the art. Module <b>211</b> may evaluate the channel quality based on the training sequence as received by device <b>200</b>. For example, module <b>211</b> may evaluate the channel quality based on a comparison of the training sequence as provided from module <b>214</b> and the predetermined training sequence.

0047According to some embodiments of the invention, module <b>211</b> may select either the frequency-multiplexing modulation method, e.g., as may be implemented by modem <b>220</b>, or the spatial-multiplexing modulation method, e.g., as may be implemented by modem <b>230</b>, based on the channel quality value. Thus, for example, the data frame may be selectively modulated using either the frequency-multiplexing modulation method or the spatial-multiplexing modulation method based on the predetermined criterion. The selection may be performed using any suitable selection method, e.g., as described below.

0048Reference is made to <figref idref="DRAWINGS">FIG. 3</figref>, which schematically illustrates a flow chart of a method of controllably selecting between the spatial-multiplexing modulation method and the frequency-multiplexing modulation method in accordance with an exemplary embodiment of the invention.

0049As indicated at block <b>302</b>, the method may include selecting a pre-determined modulation method, e.g., the spatial-multiplexing modulation method.

0050As indicated at block <b>304</b>, the channel quality corresponding to a channel estimation related to the pre-determined modulation method may be evaluated, and a channel quality value corresponding to a channel estimation related to the predetermined modulation method may be provided, e.g., as described above.

0051According to some exemplary embodiments, the channel quality may be evaluated at a predetermined time interval. For example, the channel quality may be evaluated during a channel scanning process, as is known in the art.

0052As indicated at block <b>306</b>, the method may include comparing the channel quality value to a predetermined reference quality value, e.g., a minimum quality value. A modulation method may be selected based on the comparison between the channel quality value and the reference quality value. For example, the predetermined modulation method, e.g., the spatial-multiplexing modulation method, may be selected if the channel quality value is at least equal to the reference quality value.

0053As indicated at block <b>308</b>, the frequency-multiplexing modulation method may be selected if the channel quality value is less than the reference quality value. The channel quality value corresponding to the predetermined modulation method may be re-evaluated periodically, e.g., according to the predetermined time interval, and compared to the reference quality value, as indicated at block <b>304</b>.

0054Thus, according to this exemplary embodiment, the spatial-multiplexing modulation method may be selected, e.g., by module <b>211</b> (<figref idref="DRAWINGS">FIG. 2</figref>), if the channel quality value corresponding to the spatial-multiplexing modulation method is at least equal to the reference quality value. The frequency-multiplexing modulation method may be selected, e.g., by module <b>211</b> (<figref idref="DRAWINGS">FIG. 2</figref>), if the channel quality is less than the reference quality value.

0055It will be appreciated by those skilled in the art that the device system and/or method, according to embodiments of the invention, may be implemented to achieve a relatively stable and relatively high throughput in an open environment, i.e., an environment characterized by relatively low multi-path effects, as well as in a closed environment, i.e., an environment characterized by relatively high multi-path effects. This may be achieved, for example, by selectively switching between the spatial-multiplexing modem and the frequency-multiplexing modem, as described above.

0056Embodiments of the present invention may be implemented by software, by hardware, or by any combination of software and/or hardware as may be suitable for specific applications or in accordance with specific design requirements. Embodiments of the present invention may include units and sub-units, which may be separate of each other or combined together, in whole or in part, and may be implemented using specific, multi-purpose or general processors, or devices as are known in the art. Some embodiments of the present invention may include buffers, registers, storage units and/or memory units, for temporary or long-term storage of data and/or in order to facilitate the operation of a specific embodiment.

0057While certain features of the invention have been illustrated and described herein, many modifications, substitutions changes, and equivalents may occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.