HK1157559B - Configurable contention-based period in mmwave wireless systems - Google Patents

Description

Configurable contention-based time periods in MMWAVE wireless systems

Technical Field

The field of the invention relates generally to wireless system communications and more particularly, but not exclusively, to wireless systems for transmitting and receiving millimeter wave (mmWave) signals in a WPAN/WLAN environment.

Background

Technological advances have allowed digitization and compression of large amounts of audio, video, imaging, and data information. The need to transfer data between devices in wireless mobile radio communications requires that data streams be transferred at high data rates in a variety of and dynamic environments. Wireless Personal Area Network (WPAN) communication systems are widely used for high data exchange between devices over a short distance of not more than 1 meter. Currently, WPAN systems utilize bands in the 2-7GHz band region and achieve throughputs up to several hundred Mbps (for ultra-wideband systems).

The availability of 7GHz unlicensed spectrum in the 60GHz band and advances in RF IC semiconductor technology are pushing the development of mmWave WPAN and mmWave Wireless Local Area Network (WLAN) systems that will operate in the 60GHz band and will achieve throughputs on the order of several Gbps. Currently, several standardization groups (institute of electrical and electronics engineers (IEEE)802.15.3c, IEEE 802.11ad, wireless HD SIG, ECMA TG20) are working on developing specifications for such mmWave WPAN and WLAN networks. These standards were developed primarily by introducing new PHY layers as a supplement to previous WPAN and WLAN standards, which are also attempting to reuse most of the MAC functionality. However, modifications to the MAC layer are also required to take advantage of the characteristics of certain mmWave WPANs and WLANs.

Communication links operating at 60GHz are less robust because of the inherent characteristics of high oxygen absorption and significant fading through obstructions. To meet link budget requirements, directional antennas have been envisaged for use in creating mmWave communication links. For initial device discovery, association, and synchronization, it is often required to use omni (or quasi-omni) beacons.

Disclosure of Invention

The present invention provides a method comprising: communicating in a wireless network by a Station (STA) having a Medium Access Control (MAC) layer transmitting data in a beacon interval, the beacon interval including a contention-based period to allow access to the wireless network using a carrier sense multiple access with collision avoidance (CSMA/CA) protocol, wherein the contention-based period includes a plurality of slots and a size of each slot of the plurality of slots is configurable.

The present invention also provides a method comprising: receiving, by a Station (STA) in a wireless network, a Request To Send (RTS) signal; transmitting a Clear To Send (CTS) signal from the STA; configuring the STA for a distributed mode if a Transmission Clear To Send (TCTS) signal having a bit set to a first value is received during a TCTS-to-self period (TSP); and configuring the STA for a PCP-centric mode if the TCTS signal having the bit set to a second value is received during the TSP.

The present invention also provides an apparatus comprising: a Station (STA) having a transceiver adapted to communicate in a wireless network, having a MAC layer, transmitting in a beacon interval, wherein the beacon interval includes a contention-based period to allow access to the wireless network using a carrier sense multiple access with collision avoidance (CSMA/CA) protocol, wherein the contention-based period includes a plurality of slots, and a size of each slot of the plurality of slots is configurable.

Drawings

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

fig. 1 is a block diagram illustrating an apparatus for communicating in a wireless network using very high frequency radio signals according to an embodiment of the present invention;

fig. 2 is a diagram of a beacon interval with a contention-based period and a service period according to an embodiment of the present invention;

fig. 3 is an illustration of a Discovery Beacon (DB) transmitted during a Beacon Time (BT) when an advertising beacon/frame (AB) is transmitted during an Advertising Time (AT) according to an embodiment of the present invention;

FIG. 4 is a diagram of a structure of an AB epoch (AT) in accordance with an embodiment of the present invention;

fig. 5 is a diagram of consecutive beacon intervals with contention-based time periods that may be configured with varying slot sizes and contention windows, according to an embodiment of the present invention; and

fig. 6 is a flow chart depicting a method for wireless communication in accordance with an embodiment of the present invention.

Detailed Description

In 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 skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and assemblies have not been described in detail so as not to obscure the present invention.

Embodiments of methods and apparatus for wireless communication using carrier sense multiple access with collision avoidance (CSMA/CA) periods with diversified parameters, such as slot size and contention window, described herein are described herein. In the following description, numerous specific details are set forth, such as descriptions to provide flexibility in configuring CSMS/CA periods in wireless communications based at least in part on a plurality of devices, Such As Stations (STAs) and/or Access Points (APs), and attributes of those devices, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

It would be an advance in the art to provide a scheduled access protocol for mmWave wireless devices designed to operate using local area network (WLAN) and/or Wireless Personal Area Network (WPAN) technology. Existing mmWave communication techniques and devices use a Medium Access Control (MAC) protocol employing CSMA/CA, in which contention-based channel access is performed during a contention-based period. Contention-based periods in existing mmWave communication systems include a plurality of time slots, where each time slot of the plurality of time slots is uniform in size to accommodate a particular type of communication protocol. For example, omni-directional communications by a first STA having a first transmission capability may use a first slot size, while directional communications by a second STA having a second transmission capability may use a second slot size. In addition, other CSMA/CA parameters, such as minimum and maximum contention windows, may also be changed as a function of the communication protocol. Accordingly, it would be useful to provide devices and wireless protocols configured to operate using wireless protocols that enable configurable contention-based periods (CBPs) to accommodate a set of multiple protocols and device configurations.

Embodiments of 60GHz band (57-66GHz) mmWave communication devices that provide configurable contention-based periods (CBPs) may be used in a variety of applications. Some embodiments of the invention may be used in connection with a variety of devices and systems, such as transmitters, receivers, transceivers, transmitter-receivers, wireless communication STAs, wireless communication devices, wireless Access Points (APs), modems, wireless modems, Personal Computers (PCs), desktop computers, mobile computers, laptop computers, notebook computers, tablet computers, server computers, set top boxes, handheld computers, handheld devices, Personal Digital Assistant (PDA) devices, handheld PDA devices, Mobile STAs (MSs), graphical displays, communication STAs, networks, wireless networks, Local Area Networks (LANs), Wireless LANs (WLANs), Metropolitan Area Networks (MANs), Wireless MANs (WMANs), Wide Area Networks (WANs), Wireless WANs (WWANs), according to existing IEEE 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11h, 802.11i, wireless communication STAs, wireless networks, wireless LANs, wireless MANs, devices and/or networks operating in the 802.11n, 802.11ac, 802.11ad, 802.16d, 802.16e standards and/or future versions and/or derivatives of the above and/or Long Term Evolution (LTE), Personal Area Networks (PAN), piconets, Wireless PAN (WPAN), units and/or devices that are part of the above WLAN and/or PAN and/or WPAN networks, one-way and/or two-way radio communication systems, a cellular radiotelephone communications system, a cellular telephone, a radiotelephone, a Personal Communications System (PCS) device, a PDA device incorporating a wireless communications device, a multiple-input multiple-output (MIMO) transceiver or device, a single-input multiple-output (SIMO) transceiver or device, a multiple-input single-output (MISO) transceiver or device, a Multiple Receiver Chain (MRC) transceiver or device, a transceiver or device having "smart antenna" technology or multiple antenna technologies, or the like. Some embodiments of the invention may be used with one or more types of wireless communication signals and/or systems, such as Radio Frequency (RF), Infrared (IR), Frequency Division Multiplexing (FDM), Orthogonal FDM (OFDM), Time Division Multiplexing (TDM), Time Division Multiple Access (TDMA), extended TDMA (E-TDMA), General Packet Radio Service (GPRS), extended GPRS, Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), CDMA 2000, multi-carrier modulation (MDM), discrete multi-tone (DMT), Bluetooth (RTM), ZigBee (TM), or the like. Embodiments of the invention may also be used in a variety of other devices, apparatuses, systems and/or networks.

Turning now to the drawings, fig. 1 is a block diagram illustrating devices in a wireless network 140 that communicate using extremely high frequency radio signals, such as access points (100a and 100b), mobile STAs (110a and 110b), a graphical display (120), and communication STAs (130a and 130 b). Access point 110a may communicate with another access point 110b and communication STAs (e.g., communication STAs (cs)130a and 130 b). CSs 130a and 130b may be fixed or substantially fixed devices. In some embodiments, access point 100a may communicate using mmWave signals, although the scope of the invention is not limited in this respect. Access point 100a may also communicate with other devices such as mobile STA 110a and graphical display 120. In some embodiments, access point 100a and mobile STA 110a operate as part of a peer-to-peer (P2P) network. In other embodiments, access point 100a and mobile STA 110a operate as part of a mesh network, where communications may include packets routed on behalf of other wireless devices of the mesh network (e.g., mobile STA 110 b). Fixed wireless access, wireless local area networks, wireless personal area networks, portable multimedia streaming and localization networks (e.g., in-vehicle networks) are some examples of applicable P2P and mesh networks.

Devices having a physical layer (PHY) and a Medium Access Control (MAC) layer, operating with protocols having contention-based periods that can be dynamically configured in terms of slot size and minimum/maximum contention window, such as access points (100a and 100b), mobile STAs (110a and 110b), graphical displays (120), and communication STAs (130a and 130b), may communicate using very high frequency radio signals transmitted and received through omni-directional and/or directional antennas. Communication supporting CSMA/CA as defined in IEEE 802.11 is not applicable because carrier sensing is unreliable in high frequency wireless networks 140 where directional antennas may be used. Furthermore, directionality aspects such as collision detection and resynchronization may be difficult to perform in this network 140.

Fig. 2 is an illustration of a beacon interval 200 having a contention-based period and a service period in accordance with an embodiment of the present invention. Wireless network 140, e.g., mmWave network, may be based on scheduled access, where a Personal Basic Service Set (PBSS) control point (PCP), similar to an AP, schedules times in a Beacon Interval (BI)200 for STAs, e.g., mobile STA 110, for communication. The time scheduled in the BI 200 may be allocated to Service Periods (SPs) (e.g., SP 1220 and SP 2230) and contention-based periods (e.g., CBP 1215 and CBP 2225). The scheduling of the service periods and contention-based periods in the BI 200 is transmitted in a beacon 205 or an Announcement Time (AT) 210. In the present embodiment, service periods SP 1220 and SP 2230 are owned by a single STA (e.g., mobile STA 110a), which controls access to wireless network 140 during these service periods. Alternatively, during a contention-based period (e.g., CBP 1215 and CBP 2225), multiple STAs (e.g., mobile STA 110, access point 100, and communication STA 130) may contend for access to the wireless network 140.

In an embodiment, a STA having a Medium Access Control (MAC) layer, such as mobile station 110a, may communicate in wireless network 140 and transmit data in beacon interval 200. The beacon interval 200 includes a contention-based period CBP 1215 to allow access to the wireless network via a carrier sense multiple access with collision avoidance (CSMA/CA) protocol. The contention-based period (e.g., CBP 1215 and/or CBP 2225) includes a plurality of time slots, wherein a size of each time slot of the plurality of time slots is configurable. The STA may operate as a Personal Basic Service Set (PBSS) control point (PCP) or Access Point (AP)100 to schedule time in a beacon interval 200 for communication with the STA, and wherein scheduling information for contention-based time periods is communicated in a beacon 205 or AT 210 of the beacon interval 200. Further, the STA may transmit a service period (e.g., SP 1220 and/or SP 2230) and control access to the wireless network 140 during the duration of the service period.

Fig. 3 is an illustration of a Discovery Beacon (DB) transmitted during a beacon 205 when an advertising beacon/frame (AB) is transmitted during an Advertising Time (AT)210 through a multi-level (e.g., two-level) beacon mechanism, which consists of a low-rate omni-directional discovery beacon and a high-rate directional advertising beacon/frame. The discovery beacon may only carry the necessary information to enable network entry and initialization, and this may include transmitter (e.g., MAC address) ID, timing information, association period signaling, etc. The advertising beacons carry the complete information required for normal network operation, such as channel scheduling, management and security information.

It is critical that the beacon communication (beacon) mechanism in mmWave systems should be designed in such a way as to maximize efficiency. To achieve this, embodiments of the present invention provide for the use of multi-level beacons. Specifically, for mmWave systems, an embodiment of the invention may provide a secondary beacon communication mechanism consisting of two types of beacons:

discovery Beacon (DB): this beacon is transmitted in a (low-rate) omni-directional mode. In addition to serving currently associated STAs, it also allows new STAs to discover and potentially join the network (i.e., PBSS). The DB may be a broadcast frame.

Announcement beacon/frame (AB): this beacon/frame is transmitted in a (high rate) beamforming mode. This frame/beacon may be transmitted by, for example, the PCP and the target PBSS STA that is beamformed with the PCP and may have been associated. The AB is a unicast frame addressed to a particular STA and may require the receiving STA to transmit back another frame in response to receiving the AB frame.

An additional embodiment of a beacon interval 300 is shown in fig. 3. The DB is transmitted during Discovery Time (DT) and the announcement beacon/frame is transmitted during Announcement Time (AT) 210. Data Transfer Time (DTT)320 is used for actual data communication between STAs that are part of the network, association beamforming training (a-BFT)310 is used for beamforming training in which the new STA 305 attempts to associate with the high frequency wireless network 140, and beamforming training time (BFTT)325 is used for beamforming between STAs that are already associated with the high frequency wireless network 140, such as mobile stations 100a and 110 b.

Because DB is less efficient than AB (because it is transmitted in omni-directional mode), it does not need to transmit in every beacon interval. One of the main purposes of DB and AB is synchronization. Therefore, the STAs must receive discovery beacons or announcement beacons/frames to be considered synchronized. If a STA loses multiple consecutive beacons from the PCP, it is considered unsynchronized. In this case, the STA will stop transmitting during DTT and must restart the PBSS join procedure.

While the DB is sent in omni-directional mode 330, 335 (omni/directional shown at 340), with the intent of being received by all neighbors of the PCP, the announcement frame/beacon is only delivered at high rate to a subset of the beamformed and most of the time associated STAs. This allows the PCP flexibility in balancing, for example, discovery latency and performance. Advertising beacons also contributes more to better spatial reusability, since these beacons are always transmitted in a beamformed mode and provide better efficiency when the number of antenna elements supported is higher than the number of STAs associated with the PCP.

Fig. 4 is an illustration of the structure of an AB epoch (AT)410 in which AB frames are exchanged. Each request frame shown in fig. 4 is a generic name for an AB frame and can be replaced, for example, by any management frame existing in IEEE 802.11. The request frame is a unicast and directed frame addressed to a particular STA and carries (e.g., and not by way of limitation) the channel time schedule of the network. For each request frame there must be a response from the addressed receiver. This response may be a management frame (e.g., association request, channel time allocation request), or simply an ACK if there are no management frames to transmit.

This allows PCP 420 and STA 430 to monitor and maintain a beamformed link between them, since there is a response frame for each request. If PCP 420 does not receive a response frame after it transmits a request frame to STA 430, it may conclude that the link is no longer valid and may reschedule beamforming between PCP 420 and the affected STA 430.

Multiple request/response frame exchanges can occur during AT 410. Likewise, request and response transmissions between PCP 420 and STA 430 may occur more than once on the same AT 410.

To minimize overhead associated with omni-directional transmissions, the information carried in the DB is kept to a minimum and may include PCP ID, timing information, number of remaining beacon transmissions (in the case of directional beacons), etc. In contrast, because it is transmitted in high rates, the advertising beacon/frame contains all the necessary information required to perform network functions, such as channel scheduling, control and management information, PBSS synchronization information, etc.

To improve efficiency, the DB may not exist in every beacon interval 300. If the DB is used infrequently, the PBSS performance can be substantially improved since less overhead will be paid in using low rate omni-directional transmission.

If PCP 420 wishes to serve multiple associated STAs 430 in a beacon interval 300, PCP 420 is able to transmit multiple announcement frames/beacons during the AT period of that beacon interval 300. The announcement beacon contains a beacon interval 300 time allocation that includes when the PCP 420 will be ready to receive from the STA 430 and/or transmit to the STA 430. This allows STAs 430 that receive the announcement frame/beacon to synchronize their schedule with that of the PCP 420. Finally, for STAs in power save mode, PCP 420 does not send them an announcement beacon/frame.

Fig. 5 is an illustration of successive beacon intervals including a first beacon interval 500 and a second beacon interval 550 having contention-based periods of configurable slot size and minimum/maximum contention window, in accordance with an embodiment of the present invention. In this embodiment, an STA, such as mobile station 110a of fig. 1, powers up and listens for signals from access point 100 or mobile station 110. The STA may then become a PCP and transmit a first beacon interval 500 with a scheduled contention-based time period (e.g., CBP1515, CBP2520, and CBP 3525). Scheduling information for the contention-based time period is advertised in the beacon 505 and/or AT 510, where the scheduling information includes slot size information. In this embodiment, there are two slot sizes corresponding to the PCP center slot 530 and the distributed slots 535, which are defined as:

PCP center: aLotTime aPropDiftMargin + aSortTRTSDur + aSIFSTime + aCCATime + aRxTxTxSwitchTime

Distributed: aLotTime ═ aCCATime + aPropDiftMargin + aRxTxSwitchTime + aMACProcessingDelay

The contention-based periods are slotted and the duration of each contention-based period is an integer multiple of the slot time in each contention-based period. The contention window may vary as a function of the number of devices (e.g., STAs and APs) in the wireless network 140 and the number of collisions detected in the wireless network 140. For example, the contention window may have a contention window value including a contention window minimum value and a contention window maximum value, where the boundary of the contention window has a wide separation between the minimum value and the maximum value when there are multiple collisions in the network 140. Alternatively, the contention window may be narrow if there are few collisions in the network 140.

A station, e.g., mobile station 110, may carry a contention window from a first contention-based period to a subsequent or next contention-based period in the same beacon interval 500 or a second beacon interval 550. In an embodiment, the STA initiates beamforming in a first contention-based period (e.g., CBP1515) and continues beamforming in a second contention-based period (e.g., CBP 2520) without performing CSMA/CA access in the second contention-based period.

Alternatively, if a station obtains a small contention window, it can access the same contention-based period multiple times. In addition, the size of each of the plurality of slots and the maximum contention window, the minimum contention window may be configurable based on the PCP centric CSMA/CA and distributed CSMA/CA protocols, although embodiments are not limited thereto. For example, a first slot of the plurality of slots of the contention-based period may be configured based on a PCP centric CSMA/CA protocol, and a second slot of the plurality of slots is configured on a distributed CSMA/CA protocol. Further, the size of each slot may be configured based on how Request To Send (RTS) and Clear To Send (CTS) transmissions are accomplished.

In addition, the slot size may also be affected by the antenna capabilities of the transmitting device and the receiving device. As an example, a Request To Send (RTS) signal and a Clear To Send (CTS) signal may be exchanged between STAs using multiple directional transmissions or a single quasi-omni transmission. The manner in which the RTS and CTS signals are sent and received can affect the slot size. The STA may transmit a series of beacon intervals including a first beacon interval 500 followed by a second beacon interval 550, each of which includes a beacon 505, an AT 510, a contention-based period, and a service period (not shown). In an embodiment, the STA may not complete transmission before the end of the contention-based time period (e.g., CBP1515) and may continue transmission in a subsequent contention-based time period (e.g., CBP2520 and/or CBP 3525). For example, a series of contention-based periods may be used to time synchronize the STAs, as the beamforming process may take more than one contention-based period to complete.

Fig. 6 is a flow chart depicting a method for wireless communication in accordance with an embodiment of the present invention. In element 600, a STA, e.g., mobile station 110a, scans one or more channels in wireless network 140 to determine whether one or more other devices are present. One or more access points or STAs may be present in the wireless network 140. The mobile station 110a receives a Request To Send (RTS)610 from another device, e.g., the mobile station 110b, in an Owner Access Period (OAP) of a contention-based period (CBP). Mobile station 110a sends a Clear To Send (CTS) signal to mobile station 110b in element 620. Alternatively, mobile station 110a sends a CTS to mobile station 110b and the device serving as the PCP for wireless network 140.

In element 630, the mobile station 110a receives the transmission clear to send signal (TCTS) in the TCTS to self time period (TSP). If the mobile station 110a receives the TCTS with the bit set to the first value in element 640, the STA is configured for the distributed mode in element 650. As an example, if a STA receives a TCTS with a bit set at zero in the duration field, the STA is configured for the distributed mode. In another embodiment, the bit may be set to a non-zero value in the duration field and the STAs are then configured for distributed mode. Alternatively, the bit is not set to the first value and the STA is configured for PCP centric mode in element 660. As an example, if a STA receives a TCTS with a bit set at non-zero in the duration field, the STA is configured for distributed PCP centric mode. In another embodiment, this bit may be set to zero in the duration field and the STA is then configured for PCP centric mode.

If during the TSP the STA does not receive the TCTS, the STA will use the distributed mode for access with the PCP activity field set to zero in, for example, the PBSS scheduling Information Element (IE). Also, if the PCP activity field is set to one in the PBSS schedule IE, the STA will not transmit.

Embodiments herein may be described with reference to data such as instructions, functions, procedures, data structures, applications, configuration settings, and the like. For the purposes of this disclosure, the term "program" covers a wide range of software components and constructs, including applications, drivers, processes, routines, methods, modules, and subroutines. The term "program" can be used to refer to a complete compilation unit (i.e., a collection of instructions that can be compiled independently), a collection of compilation units, or a portion of a compilation unit. Thus, the term "procedure" may be used to refer to any collection of instructions that, when executed by a STA, provide wireless communication over a contention-based period having a configurable slot size and a minimum/maximum contention window. The procedures in the STA may be considered components of the software environment.

The operations discussed herein may generally be facilitated via execution of suitable software or firmware implemented as code instructions on a host processor of the STA (as applicable). Thus, embodiments of the invention may include a set of instructions executed on some form of processing core or otherwise implemented or realized on or within a machine-readable medium. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium can comprise an article of manufacture such as Read Only Memory (ROM), Random Access Memory (RAM), magnetic disk storage media, optical storage media, and flash memory devices. Additionally, a machine-readable medium may include propagated signals such as electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.).

While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled 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.

Claims (15)

1. A method for communication, comprising:

communicating in a wireless network by a Station (STA) having a Medium Access Control (MAC) layer that transmits data in a beacon interval, the beacon interval including a contention-based period, to allow access to the wireless network using a carrier sense multiple access with collision avoidance (CSMA/CA) protocol, wherein the contention-based time period comprises a plurality of time slots and a size of each time slot of the plurality of time slots is configurable, and wherein the STA functions as a Personal Basic Service Set (PBSS) control point (PCP) or Access Point (AP) to schedule time in the beacon interval for communication with the STA, and wherein scheduling information for the contention-based time period is transmitted in an Announcement Time (AT) of the beacon interval or a beacon, the scheduling information including a size of each of the plurality of time slots.

2. The method of claim 1, further comprising transmitting a service period, wherein the STA controls access to the wireless network during a duration of the service period.

3. The method of claim 1, wherein a size of each of the plurality of slots and a minimum and maximum contention window are configurable based on a PCP centric CSMA/CA and distributed CSMA/CA protocol.

4. The method of claim 3, wherein a first time slot of the plurality of time slots of the contention-based period is configured based on the PCP centric CSMA/CA protocol and a second time slot of the plurality of time slots is configured based on the distributed CSMA/CA protocol.

5. The method of claim 4, further comprising configuring a size of each of the plurality of time slots based on how Request To Send (RTS) and Clear To Send (CTS) transmissions are completed.

6. The method of claim 1, wherein minimum and maximum contention windows for each contention-based period are configurable, and wherein the STA serves as a Personal Basic Service Set (PBSS) control point (PCP) or Access Point (AP), and the STA chooses minimum and maximum contention window values based on a number of collisions detected in the wireless network or a number of associated stations in the wireless network.

7. The method of claim 1, further comprising transmitting the data over a second beacon interval.

8. The method of claim 7, wherein the STA initiates beamforming in the contention-based period and continues the beamforming in a second contention-based period without performing CSMA/CA access in the second contention-based period.

9. An apparatus for communication, comprising:

a Station (STA) having a transceiver adapted to communicate in a wireless network, having a MAC layer, transmits in a beacon interval, wherein the beacon interval includes a contention-based period to allow access to the wireless network using a carrier sense multiple access with collision avoidance (CSMA/CA) protocol, wherein the contention-based period of time comprises a plurality of time slots, and a size of each time slot of the plurality of time slots is configurable, and wherein the STA functions as a Personal Basic Service Set (PBSS) control point (PCP) or Access Point (AP) to schedule time in the beacon interval for communication with the STA, and wherein scheduling information for the contention-based time period is transmitted in an Announcement Time (AT) of the beacon interval or a beacon, the scheduling information including a size of each of the plurality of time slots.

10. The apparatus of claim 9, wherein a size of each of the plurality of slots and a minimum and maximum contention window are configurable based on a PCP-centric CSMA/CA and a distributed CSMA/CA protocol.

11. The apparatus of claim 10, wherein a first time slot of the plurality of time slots of the contention-based period is configured based on the PCP centric CSMA/CA protocol and a second time slot of the plurality of time slots is configured based on the distributed CSMA/CA protocol.

12. The apparatus of claim 11, further comprising configuring a size of each of the plurality of time slots based on how Request To Send (RTS) and Clear To Send (CTS) transmissions are completed.

13. The apparatus of claim 9, wherein minimum and maximum contention windows for each contention-based period are configurable, and wherein the STA serves as a Personal Basic Service Set (PBSS) control point (PCP) or Access Point (AP), and the STA chooses minimum and maximum contention window values based on a number of collisions detected in the wireless network or a number of associated stations in the wireless network.

14. The device of claim 9, further comprising transmitting data over a second beacon interval.

15. The apparatus of claim 14, wherein the STA initiates beamforming in the contention-based period and continues the beamforming in a second contention-based period without performing CSMA/CA access in the second contention-based period.