Communicating over a wireless link using a data container structure that has partitions of different types

TECHNICAL FIELD

0001The invention relates generally to communicating, in a given session over a wireless link, a data container structure that includes partitions of different types.

BACKGROUND

0002Various wireless access technologies have been proposed or implemented to enable mobile stations to communicate with other mobile stations or with wired terminals coupled to wired networks. Examples of wireless access technologies include GSM (Global System for Mobile communications) or UMTS (Universal Mobile Telecommunications System) technologies, defined by the Third Generation Partnership Project (3GPP); CDMA 2000 (Code Division Multiple Access 2000) technologies, defined by 3GPP2; or other wireless access technologies.

0003Another type of wireless access technology is the WiMax (Worldwide Interoperability for Microwave Access) technology. WiMax is based on the IEEE (Institute of Electrical and Electronics Engineers) 802.16 standards. The WiMax wireless access technology is designed to provide wireless broadband access.

0004To support even higher data rates, the IEEE is also developing a new wireless standard referred to as IEEE 802.16m. It is anticipated that 802.16m is able to support wireless data rates of up to 1 gigabits per second (Gbps). The ability to reach such high data rates is based on the use of multiple input, multiple output (MIMO) technology. MIMO refers to the use of multiple antennas at the transmit side and at the receive side, such that data can be transmitted from multiple antennas of a transmitter over multiple paths for receipt by antennas of a receiver.

0005As new wireless access technologies such as IEEE 802.16m are developed, wireless access networks have to address the issue of presence of both legacy mobile stations and mobile stations that support a new wireless access technology. For example, in a WiMax wireless access network, once 802.16m is implemented, it is likely that the WiMax wireless access network would have to support communications with both legacy WiMax mobile stations (those mobile stations that support IEEE 802.16e access, for example) and 802.16m mobile stations. If both legacy mobile stations and 802.16m mobile stations are present, a base station that supports wireless access by such mobile stations would have to handle both uplink and downlink data exchanged between the different types of mobile stations and the base station. However, conventionally, an efficient mechanism has not been proposed or defined to enable efficient wireless communication with legacy WiMax mobile stations and 802.16m mobile stations.

SUMMARY

0006In general, according to an embodiment, to improve efficiency in communicating data with different types of mobile stations, a data container structure is communicated over a wireless link, where the data container structure includes a configurable concatenation of partitions of different types that carry data of the different types of mobile stations.

0007Other or alternative features will become apparent from the following description, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

0008<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram of a communications network that includes a wireless access network that supports different types of mobile stations (legacy mobile stations and new technology mobile stations), in accordance with preferred embodiments of the invention.

0009<figref idref="DRAWINGS">FIGS. 2 and 3</figref> illustrate frames of types 1 and 2, in accordance with a preferred embodiment.

0010<figref idref="DRAWINGS">FIG. 4</figref> illustrates a superframe that includes a concatenation of frames of type 1 and frames of type 2, in accordance with a preferred embodiment.

0011<figref idref="DRAWINGS">FIGS. 5 and 6</figref> illustrate frames of types 1 and 2, in accordance with another preferred embodiment.

0012<figref idref="DRAWINGS">FIG. 7-9</figref> illustrate superframes according to further preferred embodiments.

DETAILED DESCRIPTION

0013In the following description, numerous details are set forth to provide an understanding of some embodiments. However, it will be understood by those skilled in the art that some embodiments may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

0014In general, according to preferred embodiments, a technique or mechanism is provided to wirelessly communicate data associated with different types of mobile stations, where the data is carried in a flexible hybrid data container structure including a configurable concatenation of different types of partitions. The data container structure in some preferred embodiments is referred to as a “superframe,” where a “superframe” refers to any data structure that contains multiple partitions (sometimes referred to as “frames”) of data. In the ensuing discussion, reference is made to flexible hybrid superframes that contain configurable concatenations of frames of different types—it is noted that the same or similar techniques can be applied to other types of flexible hybrid data container structures and partitions.

0015The different types of frames in the superframe can be used to carry uplink data (from mobile station to base station) and downlink data (from base station to mobile station), as well as to carry control information. Collectively, uplink/downlink data and control information can be referred to as “information.” Uplink or downlink “data” refers to bearer traffic, such as voice or packet data, as examples.

0016Different types of mobile stations refer to mobile stations that operate according to different wireless access technologies. In one specific example, one wireless access technology is the WiMax (Worldwide Interoperability for Microwave Access) technology, as defined by the IEEE (Institute of Electrical and Electronics Engineers) 802.16 standards, including the IEEE 802.16e standard. Another wireless access technology is the 802.16m technology.

0017The frames of different types contained in a hybrid superframe can have different structures. For example, a superframe can include at least one first frame of a first type having a first structure, and at least one second frame of a second type having a second, different structure. The number of first frames and number of second frames are configurable to provide flexibility.

0018In a preferred embodiment, the hybrid superframe includes at least one first frame of a first type that contains time division multiplexed data, and a second frame of a second type that contains frequency division multiplexed data. Each of the frames is able to carry data of different types of mobile stations, such as WiMax mobile stations and 802.16m mobile stations. Note that reference to specific standards is provided for purposes of explanation, as embodiments of the invention can cover wireless access technologies according to other standards.

0019“Time division multiplexed” data refers to data having multiple portions that are communicated (multiplexed) in multiple time slots. An example of time multiplexed data includes a first data portion being communicated in a first time slot on a given carrier, and a second data portion communicated in a second time slot in the same carrier.

0020“Frequency division multiplexed data” refers to data having multiple portions communicated on different carriers of different frequencies. Thus, for example, a first data portion is communicated in a first carrier of a first frequency, and a second data portion is communicated in a second carrier of a second frequency. In the WiMax context, “frequency division multiplexed data” refers to data having multiple portions communicated on different subcarriers of different frequencies. The terms “carrier” and “subcarrier” are used interchangeably.

0021In the above embodiment, the concatenated different types of frames in the superframe are frames that use different multiplexing schemes (a first frame that contains time division multiplexed data and a second frame that contains frequency division multiplexed data).

0022In another preferred embodiment, the concatenated frames of a hybrid superframe can include at least one first frame (of type 1) having a single downlink subframe (to communicate downlink information that includes uplink control and downlink control and data) and a single uplink subframe (to communicate uplink information), and at least one second frame (of type 2) having flexible and variable numbers of uplink and downlink subframes.

0023A frame of type 2 can have subframes of unequal lengths such that there is flexibility in the number of uplink and downlink subframes that can be provided in a frame. For example, a frame can have one or more uplink subframes and one or more downlink subframes. A first frame can have different numbers of uplink subframes and/or downlink subframes than a second frame. The lengths of the subframes (uplink and/or downlink) are variable such that more than one uplink subframe and/or more than one downlink subframe can be fit into a frame. This flexibility in defining subframes of a frame allows for better wireless communication performance with lower latency and higher throughput.

0024In accordance with preferred embodiments, the ability to include frames of different types within a hybrid superframe allows for more flexible and efficient communication of data in a wireless access network that has to support different types of mobile stations, including legacy mobile stations and new technology mobile stations. A “legacy” mobile station refers to a mobile station that operates according to an older wireless access technology, whereas “new technology mobile station” refers to a mobile station that operates according to a more recent (or newer) wireless access technology. In one example, a legacy mobile station refers to a mobile station that operates according to the WiMax wireless access technology (e.g., as defined by IEEE 802.16e), whereas a new technology mobile station refers to a mobile station that operates according to the IEEE 802.16m wireless access technology. More generally, instead of referring to legacy mobile stations and new technology mobile stations, reference can be made to different types of mobile stations that support different types of wireless access technologies.

0025In the ensuing discussion, reference is made to legacy or WiMax mobile stations and to 802.16m mobile stations. However, the same techniques according to preferred embodiments can be used with mobile stations that operate according to other wireless access technologies.

0026<figref idref="DRAWINGS">FIG. 1</figref> illustrates a communications network that includes a wireless access network <b>100</b> that has a base station <b>104</b> associated with a coverage area <b>102</b>. The wireless access network <b>100</b> includes multiple base stations associated with respective coverage areas.

0027The base station <b>104</b> is able to communicate with mobile stations <b>106</b>A and <b>106</b>B in the coverage area <b>102</b> of the base station <b>104</b>. The base station <b>104</b> is able to support communications with both legacy mobile stations, such as legacy mobile station <b>106</b>A, and 802.16m mobile station <b>106</b>B.

0028The base station <b>104</b> can include a base transceiver station (BTS) to perform radio frequency (RF) communications with mobile stations in the coverage area <b>102</b>. Also, the base station <b>104</b> can include a base station controller or radio network controller for controlling tasks associated with the base station.

0029As further depicted in <figref idref="DRAWINGS">FIG. 1</figref>, the base station <b>104</b> is connected to a system controller <b>108</b>. If the wireless access network <b>100</b> is a WiMax access network, as defined by the IEEE 802.16 standards, then the system controller <b>108</b> can be an access service network (ASN) gateway. The system controller <b>108</b> is in turn connected to a gateway node <b>110</b>, which connects the wireless access network <b>100</b> to an external network <b>112</b>, such as the Internet. In the WiMax context, the gateway node <b>110</b> is referred to as a connectivity service network (CSN) node.

0030As further depicted in <figref idref="DRAWINGS">FIG. 1</figref>, the base station <b>104</b> can include software <b>120</b> executable on one or more central processing units (CPUs) <b>122</b>, which is (are) connected to a storage <b>124</b>. The base station <b>104</b> includes an air interface <b>126</b> to wirelessly communicate with mobile stations, and a network interface <b>128</b> to communicate with the system controller <b>108</b>.

0031The software <b>120</b> depicted in <figref idref="DRAWINGS">FIG. 1</figref> is representative of various software modules that are provided in the base station <b>104</b>, including software modules in the data plane and control plane of the base station <b>104</b>. Among the tasks that can be performed by the software <b>120</b> of the base station <b>104</b> is the ability to communicate data in superframes according to preferred embodiments. The software <b>120</b> can also include a scheduler to schedule communication of data associated with different mobile stations. Note that each mobile station <b>106</b>A or <b>106</b>B can similarly include software executable on CPU(s) that is (are) connected to storage.

0032<figref idref="DRAWINGS">FIG. 2</figref> shows frames <b>200</b> (<b>200</b>A and <b>200</b>B depicted) of type 1. Each frame <b>200</b> includes a downlink subframe (to carry downlink information from the base station to the mobile stations) and an uplink subframe (to carry uplink information from mobile stations to the base station). The frame duration (or frame length) of each frame starts at the beginning of a legacy preamble in the frame and ends at the beginning of a legacy preamble in the next frame. For example, in <figref idref="DRAWINGS">FIG. 2</figref>, the frame duration of frame <b>200</b>A starts at the beginning of the legacy preamble <b>202</b> contained in the frame <b>200</b>A, and ends at the beginning of the next legacy preamble <b>202</b> contained in the next frame <b>200</b>B. Each of the frames <b>200</b>A and <b>200</b>B can be referred to as legacy frames (since they are defined between legacy preambles).

0033Generally, the legacy preamble is provided on the downlink by a base station and contains control information to allow a mobile station to acquire a wireless signal and to synchronize the mobile station with the base station. The preamble can also include information that identifies the modulation scheme, transmission rate, and length of time to transmit the entire frame. In addition, the legacy preamble can include a frame control header and downlink/uplink MAP information that defines resources to be used for downlink and uplink communications, and the modulation and coding schemes included in scheduling grants. A legacy preamble is a preamble defined by IEEE 802.16e, in one exemplary embodiment.

0034The legacy preamble <b>202</b> in the frame <b>200</b>A is contained in the downlink subframe of the frame <b>200</b>A. The downlink subframe of the frame <b>200</b>A also includes the following: a segment <b>204</b> to carry legacy downlink data (downlink data for legacy mobile stations) that is transmitted from the base station to the mobile stations; a 802.16m preamble <b>206</b>, which is a preamble defined by IEEE 802.16m; and a segment <b>208</b> that includes both legacy and 802.16m downlink data.

0035The 802.16m preamble <b>206</b> can include downlink map (DL-MAP) information that defines resources to be used for communicating downlink data from the base station to the mobile stations. The DL-MAP information provides information regarding start times for transmission of downlink data to specific mobile stations by the base station. The 802.16m preamble <b>206</b> can also include a preamble sequence and/or a synchronization channel to support 802.16m mobile stations.

0036As depicted in <figref idref="DRAWINGS">FIG. 2</figref>, a 16 m frame can be defined between two consecutive 16 m preambles—as depicted in <figref idref="DRAWINGS">FIG. 2</figref>, such a 16 m frame is offset (shifted) with respect to the legacy frames <b>200</b>A, <b>200</b>B.

0037The resources on which downlink legacy and 802.16m data in the segment <b>208</b> of the downlink subframe are carried can be specified by a scheduler in the base station. The assigned resources used to carry the downlink legacy and 802.16m data to the mobile stations are identified in the DL-MAP information provided to the mobile stations in the 802.16m preamble <b>206</b>.

0038Following the downlink subframe, a gap <b>210</b> is provided that represents the switching time between the communication of downlink data and the communication of uplink data. Following the gap <b>210</b>, an uplink subframe <b>212</b> is communicated that contains uplink data for both legacy and 802.16m mobile stations. Again, the resources at which mobile stations can transmit the uplink data of the uplink subframe <b>212</b> are determined by the scheduler in the base station. Following the uplink subframe, another gap <b>214</b> is provided to switch between uplink transmission and downlink transmission in the subsequent frame <b>200</b>B.

0039As shown in <figref idref="DRAWINGS">FIG. 2</figref>, each frame <b>200</b> of type 1 has one downlink subframe and one uplink subframe.

0040<figref idref="DRAWINGS">FIG. 3</figref> shows frames <b>300</b> (<b>300</b>A and <b>300</b>B depicted) of type 2. Within each frame <b>300</b>, there can be more than one downlink subframe and/or more than one uplink subframe. In fact, as shown in <figref idref="DRAWINGS">FIG. 3</figref>, the downlink and uplink subframes can be defined to have varying length such that there is flexibility in the number of downlink and uplink subframes included within a legacy frame (<b>300</b>A or <b>300</b>B). The legacy frame <b>300</b>A has two switching points (for switching between uplink and downlink transmissions), and the legacy frame <b>300</b>B has four switching points.

0041The frame <b>300</b>A includes a first downlink subframe that includes segments <b>308</b>, <b>310</b>, <b>304</b>, and <b>312</b> (segment <b>308</b> is a legacy preamble, segment <b>310</b> carries legacy downlink data, segment <b>304</b> carries a 802.16m preamble, and segment <b>312</b> carries both legacy and 802.16m downlink data). After a gap <b>314</b> (corresponding to a downlink-uplink switching point), an uplink subframe <b>316</b> is provided in the frame <b>300</b>A, where the uplink subframe <b>316</b> carries both legacy and 802.16m uplink data. Following another gap <b>318</b> (corresponding to an uplink-downlink switching point), a second downlink subframe is provided, where the second downlink subframe includes a 802.16m preamble <b>306</b>, and a segment <b>320</b> containing 802.16m downlink data.

0042As depicted, the three subframes in the frame <b>300</b>A are of different lengths.

0043The frame duration of each legacy frame <b>300</b> is the same frame duration as each legacy frame <b>200</b> in <figref idref="DRAWINGS">FIG. 2</figref>; in other words, the frame duration of each legacy frame <b>300</b> is defined between the beginning of one legacy preamble and the beginning of the next legacy preamble. However, in addition to this legacy frame structure (having frame duration defined by legacy preambles), each legacy frame <b>300</b> also contains a 802.16m frame <b>302</b>A (<figref idref="DRAWINGS">FIG. 3</figref>), which is of shorter length than the legacy frame.

0044The shorter-duration 802.16m frame <b>302</b>A is defined between the beginning of a first 802.16m preamble <b>304</b> and the beginning of the next 802.16m preamble <b>306</b>. Note that both 802.16m preambles <b>304</b> and <b>306</b> are provided in the same frame <b>300</b>A. The second frame <b>300</b>B shown in <figref idref="DRAWINGS">FIG. 3</figref> also similarly includes two 802.16m preambles <b>332</b> and <b>336</b> that define a respective 802.16m frame. Also, note that as depicted in <figref idref="DRAWINGS">FIG. 3</figref>, two consecutive 802.16m frames <b>302</b>A and <b>302</b>B are provided within the duration of one legacy frame, except that the two consecutive 802.16m frames <b>302</b>A and <b>302</b>B are offset with respect to each legacy frame. The 802.16m frame <b>302</b>B is defined between 16 m preambles <b>306</b> and <b>332</b>.

0045The second frame <b>300</b>B includes a first downlink subframe that includes the legacy preamble <b>322</b>; a first uplink subframe <b>326</b> that contains 802.16m uplink data; a second downlink subframe that includes a legacy downlink data segment <b>330</b>, the 802.16m preamble <b>332</b>, and a segment <b>334</b> carrying legacy and 802.16m downlink data; a second uplink subframe <b>338</b> that carries legacy and 802.16m uplink data; and a third downlink subframe that includes the 802.16m preamble <b>336</b> and a 802.16m downlink data segment <b>340</b>.

0046Gaps <b>324</b>, <b>328</b>, <b>342</b>, and <b>344</b> are provided between respective pairs of uplink and downlink subframes to switch between uplink and downlink transmissions.

0047In accordance with some embodiments, as depicted in <figref idref="DRAWINGS">FIG. 4</figref>, a hybrid superframe <b>350</b> can include a configurable concatenation of frames <b>200</b> of type 1 and frames <b>300</b> of type 2. More specifically, the superframe <b>350</b> can include X number of frames <b>200</b> of type 1 (X≧1) and Y number of frames <b>300</b> of type 2 (Y≧1). Even more generally, the superframe <b>350</b> can include X number of frames <b>200</b> of type 1 (X≧0) and Y number of frames <b>300</b> of type 2 (Y≧0). The values of X and Y are configurable based on the number of legacy and 802.16m mobile stations in a particular coverage area that is served by a base station. The ability to flexibly concatenate different frame types into one superframe provides enhanced flexibility to allow for more efficient support of both legacy and 802.16m wireless communications by a base station.

0048For <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, it is assumed that the base station has one base station transceiver that supports both legacy and 802.16m communication. In a different embodiment, the base station can include a first dedicated transceiver for supporting legacy communications, and a second transceiver for supporting 802.16m communications. <figref idref="DRAWINGS">FIGS. 5 and 6</figref> illustrate frames of type 1 and frames of type 2 for the scenario where the base station includes separate, dedicated transceivers for legacy and 802.16m wireless communications. As depicted in <figref idref="DRAWINGS">FIG. 5</figref>, the frames <b>400</b> of type 1 include a first frame <b>400</b>A and second frame <b>400</b>B. The structure of each frame <b>400</b> is the same structure as frame <b>200</b> depicted in <figref idref="DRAWINGS">FIG. 2</figref>.

0049However, the structure of frames <b>500</b> of type 2 (<b>500</b>A and <b>500</b>B depicted in <figref idref="DRAWINGS">FIG. 6</figref>) is different from the structure of frames <b>300</b> depicted in <figref idref="DRAWINGS">FIG. 3</figref>. As with frame <b>300</b> in <figref idref="DRAWINGS">FIG. 3</figref>, each frame <b>500</b> in <figref idref="DRAWINGS">FIG. 6</figref> can include more than one downlink subframe and/or more than one uplink subframe. Also, each frame <b>500</b> includes two 802.16m preambles that define a 802.16m frame structure of a shorter length (represented as <b>502</b> in <figref idref="DRAWINGS">FIG. 6</figref>) than the legacy frame structure <b>500</b> (similar to the structure shown in <figref idref="DRAWINGS">FIG. 3</figref>).

0050A difference between the frame <b>500</b> in <figref idref="DRAWINGS">FIG. 6</figref> and the frame <b>300</b> in <figref idref="DRAWINGS">FIG. 3</figref> is that in each frame <b>500</b>, under certain conditions, no switching gaps need be provided when switching between uplink and downlink transmissions of data according to different technologies (legacy versus 802.16m). One example of this occurs between a segment <b>504</b> containing legacy uplink data followed by a downlink 802.16m preamble <b>506</b>. Normally, if the same transceiver was used to perform both legacy and 802.16m transmissions, a gap would have to be provided between segments <b>504</b> and <b>506</b>. However, since dedicated transceivers are provided in the base station for respective legacy and 802.16m communications, the legacy transceiver can be used to transmit the legacy uplink data in segment <b>504</b>, and the 802.16m transceiver can be used to transmit the 802.16m preamble <b>506</b> immediately after the legacy uplink data segment <b>504</b>. By avoiding switching gaps under certain conditions, more information can be sent in each frame <b>500</b> for enhanced bandwidth efficiency.

0051Another example where a switching gap is not needed is between transmission of a 802.16m uplink data segment <b>508</b> and a legacy downlink data segment <b>510</b> in frame <b>500</b>B.

0052A hybrid superframe can include a configurable concatenation of X number of frames <b>400</b> of type 1, and Y number of frames <b>500</b> of type 2.

0053In accordance with alternative preferred embodiments, a superframe can include a concatenation of other types of frames, where in some of the frames, legacy data and 802.16m data are provided in time division multiplexed (TDM) manner, and where in other frames, legacy data and 802.16m data are provided in a frequency division multiplexed (FDM) manner.

0054For example, as shown in <figref idref="DRAWINGS">FIG. 7</figref>, a first frame <b>600</b> can include a downlink subframe <b>616</b> and an uplink subframe <b>604</b>. In the uplink subframe <b>604</b>, the legacy and 802.16m uplink data are divided into distinct TDM subpartitions <b>608</b> and <b>610</b>. The TDM subpartition <b>608</b> includes time slots carrying just legacy uplink data, and the TDM subpartition <b>610</b> includes time slots carrying just 802.16m uplink data. In this first frame <b>600</b>, the legacy data and 802.16m data in the downlink subframe <b>616</b> are also provided in distinct TDM subpartitions <b>620</b> and <b>622</b>. Alternatively, instead of providing legacy data and 802.16m data in distinct TDM subpartitions, the legacy data and 802.16m data can be mixed and communicated based on scheduling.

0055In a second frame <b>602</b>, a downlink subframe <b>624</b> also includes legacy data and 802.16m data in distinct TDM subpartitions <b>628</b> and <b>630</b>. However, an uplink subframe <b>606</b> in the second frame <b>602</b> includes distinct FDM subpartitions <b>612</b> and <b>614</b> for carrying respective legacy and 802.16m uplink data. The uplink FDM subpartition <b>612</b> includes a group of subcarriers that carry legacy uplink data, and the uplink FDM subpartition <b>614</b> includes another group of subcarriers that carry 802.16m uplink data.

0056The first frame <b>600</b> thus includes a TDM downlink subframe <b>616</b> and a TDM uplink subframe <b>604</b>, and the second frame <b>602</b> includes a TDM downlink subframe <b>624</b> and an FDM uplink subframe <b>606</b>.

0057In an alternative embodiment, it may also be possible to configure one of the downlink subframes <b>616</b> and <b>624</b> to carry FDM data.

0058Together, the concatenated frames <b>600</b> and <b>602</b> make up a hybrid superframe. The superframe has a superframe preamble <b>618</b> that is provided at the beginning of the downlink subframe <b>616</b> in the first frame <b>600</b>. The preamble <b>618</b> includes a superframe header as well as a legacy preamble. The superframe header, which can be communicated through a broadcast control channel (BCCH), for example, can specify whether uplink TDM and uplink FDM subframes are to be used. Also, within each downlink or uplink subframe, the superframe can specify the legacy-to-16 m partition ratio to specify the amount of each subframe to allocate to legacy data versus 802.16m data. Also, the superframe header can specify the number of downlink/uplink switching points per frame. Typically, the number of switching points between uplink and downlink data is two, although a greater number can be supported in other implementations.

0059The superframe depicted in <figref idref="DRAWINGS">FIG. 7</figref> includes type 1 frames <b>600</b> and <b>602</b>. A superframe depicted in <figref idref="DRAWINGS">FIG. 8</figref>, on the other hand, contains a concatenation of both type 1 frames and type 2 frames. In <figref idref="DRAWINGS">FIG. 8</figref>, a frame <b>700</b> is a type 1 frame, while frames <b>702</b>A and <b>702</b>B are each type 2 frames. In each frame <b>702</b> (<b>702</b>A or <b>702</b>B), a subframe of a shorter duration can be specified, such as uplink subframe <b>704</b> (which has a shorter duration than the downlink subframe <b>706</b>, which has the same length as each of the subframes in the type 1 frame <b>700</b>. In each frame <b>702</b> of type 2, an uplink subframe can be either an uplink TDM subframe or an uplink FDM subframe.

0060The superframes depicted in <figref idref="DRAWINGS">FIGS. 7 and 8</figref> assume a scenario in which the same base station transceiver is used to support both legacy and 802.16m communications. <figref idref="DRAWINGS">FIG. 9</figref> shows a scenario in which distinct base station transceivers are used to support legacy and 802.16m communications. In <figref idref="DRAWINGS">FIG. 9</figref>, a frame <b>800</b> of type 1 has the same structure as the frame <b>700</b> of type 1 in <figref idref="DRAWINGS">FIG. 8</figref>. The structure of the frame <b>802</b>A of type 2 is also the same structure as the frame <b>702</b>A of type 2 in <figref idref="DRAWINGS">FIG. 8</figref>. However, in frame <b>802</b>B of type 2 in <figref idref="DRAWINGS">FIG. 9</figref>, a switching gap can be omitted when switching between transmission of a 802.16m uplink data segment <b>804</b> and transmission of a legacy downlink data segment <b>806</b>, similar to the omission of switching gaps in the frames <b>500</b>A and <b>500</b>B of <figref idref="DRAWINGS">FIG. 6</figref>.

0061The flexible hybrid superframes discussed above enable an efficient manner to evolve from legacy wireless access communications to an advanced wireless access communications. As the number of legacy mobile stations in the wireless network varies depending upon the deployment, the frame structure configuration can be changed relatively easily to accommodate such varying number of legacy mobile stations. Also, system performance can be optimized by using either uplink TDM or uplink FDM subframes. Also, flexibility is provided in defining the number of switching points between uplink and downlink transmissions. For example, the re-transmission delay (delay between transmission of original data and re-transmission of the data due to a negative acknowledgment) can be made lower with a greater number of downlink/uplink switching points. Reduced latency leads to improved quality of service.

0062The tasks involved in communicating data in superframes according to preferred embodiments can be controlled by software. Instructions of such software are executed on a processor (e.g., CPU <b>122</b> in <figref idref="DRAWINGS">FIG. 1</figref>). The processor includes microprocessors, microcontrollers, processor modules or subsystems (including one or more microprocessors or microcontrollers), or other control or computing devices. A “processor” can refer to a single component or to plural components.

0063Data and instructions (of the software) are stored in respective storage devices, which are implemented as one or more computer-readable or computer-usable storage media. The storage media include different forms of memory including semiconductor memory devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable and programmable read-only memories (EPROMs), electrically erasable and programmable read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy and removable disks; other magnetic media including tape; and optical media such as compact disks (CDs) or digital video disks (DVDs).

0064In the foregoing description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details. While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.