1. Field of the Invention
The invention relates to wireless transmission of data information, and in particular, to wireless transmission of delay insensitive uncompressed data over a wireless network.
2. Brief Description of the Related Technology
High definition (HD) television has been well received by consumers and now many HD components are available. The high-definition multimedia interface (HDMI) standard has been developed to allow compatible interfaces between components. The next stage is to allow consumers to connect HD components across a short range wireless network. To achieve real-time video transfer, the video is transmitted in uncompressed form.
Time insensitive data transfer such as file transfer is a very important application for high data rate wireless networks designed for downloading/uploading compressed/uncompressed video files or other data files over short ranges. Even though such applications are delay insensitive, an efficient transmission scheme can significantly enhance the channel efficiency. For battery operated devices, reduction in data transfer time results in a longer battery life.
A high-rate PHY (HRP) frame format has not been defined for such networks. A HRP composite frame format for uncompressed video is defined as illustrated in
One aspect of the invention provides a method of transferring data in a wireless communication network for uncompressed video. The method includes: fragmenting the data into a plurality of data packets; appending a PHY header to at least one of the data packets to form a medium access control (MAC) frame; setting a field in the PHY header to indicate that the packets do not contain audio video (A/V) data; and transmitting the MAC frame to another device in the wireless communication network.
After the data has been transmitted, transmitting may packetize uncompressed video with the MAC frame and setting the field of the PHY header to indicate A/V data is being transferred.
The method may further include fragmenting at least one of the data packets into a predetermined number of sub-packets, wherein the predetermined number of sub-packets when the sub-packets do not contain A/V data is different from the number of the sub-packets when the A/V data is transferred. The predetermined number of sub-packets may be same as a number of acknowledgment (ACK) groups in the another device such that a PHY layer in the other device does not apply an acknowledgment group mapping for mapping the sup-packets to the ACK groups. Each ACK group may be appended by a cyclic redundancy checksum (CRC), wherein the CRC is handled by the PHY layer. All the sub-packets in an ACK group may be moved to a MAC layer in a receiver side by a PHY layer of the receiver side. The MAC layer may selectively select sub-packets whose own CRCs are correct.
The method may further include a retransmission indicator field configured to indicate the retransmission status of each sub-packet. The method may further include appending a MAC header to at least one of the data packets to form the MAC frame. Each of the sub-packets may include own MAC header such that errors in one MAC header do not affect other sub-packets. The sub-packets may share one MAC header.
The A/V data may include video, audio, and control. The MAC frame may include a MAC header, wherein the MAC frame further comprises a header CRC for the PHY header and the MAC header.
Each of the plurality of data packets may include a sub-packet, and wherein the sub-pack comprises a plurality of small payloads. Each of the small payloads may include a sub-sub-packet. Each of the small payloads may include a payload header comprising fields for length, sequence number, fragment control, CRC, and MSDU. Each of the small payloads may include a known pattern.
The PHY and MAC headers may be designed to fit into 3 orthogonal frequency division multiplexing (OFDM) symbols.
Another aspect of the invention provides a system for transferring data in a wireless communication network for uncompressed video. The system includes: a transmitter configured to receive data and generate a plurality of medium access control (MAC) frame according to a first format, the transmitter comprising a physical (PHY) layer and a MAC layer; and a receiver configured to receive the plurality of MAC frame from the transmitter and extract original data according to the first format, comprising a physical (PHY) layer and a medium access control (MAC) layer. The MAC frame comprises a field to indicate that data packets in the MAC frame do not contain audio video (A/V) data.
After the data has been transmitted, the MAC frame may contain uncompressed video and the field of the MAC frame is set to indicate A/V data is being transferred, and the transmitter and the receiver may use a second format of the MAC frame.
The transmitter may further include a detector configured to detect whether the data contains the A/V data and a controller to set the field of the MAC frame according to a signal from the detector.
Still another aspect of the invention provides a system for transferring data in a wireless communication network for uncompressed video. The system includes: a transmitter configured to receive data and generate a plurality of medium access control (MAC) frame according to a first format, the transmitter comprising a physical (PHY) layer and a MAC layer; and a receiver configured to receive the plurality of MAC frame from the transmitter and extract original data according to the first format, comprising a physical (PHY) layer and a medium access control (MAC) layer. The data packets in the MAC frame do not contain audio video (A/V) data.
Still another aspect of the invention provides a system for transferring data in a wireless communication network for uncompressed video. The system includes: means for fragmenting the data into a plurality of data packets; means for appending a PHY header to at least one of the data packets to form a medium access control (MAC) frame; means for setting a field in the PHY header to indicate that the packets do not contain audio video (A/V) data; and means for transmitting the MAC frame to another device in the wireless communication network.
The following detailed description of certain embodiments presents various descriptions of specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways as defined and covered by the claims. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout.
The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner, simply because it is being utilized in conjunction with a detailed description of certain specific embodiments of the invention. Furthermore, embodiments of the invention may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the inventions herein described.
Overview of Communication System
Certain embodiments provide a method and system for transmission of uncompressed HD video information from a transmitter to a receiver over wireless channels.
A wireless video area network (WVAN) consists of one Coordinator and one or more Stations as shown in
The computing and networking industry uses the Open Systems Interconnection Reference Model (OSI model) for communications and computer network protocol design. The OSI model is a hierarchical structure of seven layers that defines the requirements for communications between two devices. The seven layers include application layer, presentation layer, session layer, transport layer, network layer, data link layer, physical layer.
Of particular relevance here are the data link and physical layers. The data link layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer. The data link layer is divided into two sublayers: the Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking. The physical (PHY) layer defines all the electrical and physical specifications for devices.
The high-rate PHY (HRP) is a PHY that supports multi-Gb/s throughput at distance of about 10 m through adaptive antenna technology. Because of this, the HRP is highly directional and can only be used for unicast connections as shown in
The low-rate PHY (LRP) is a multi-Mb/s bidirectional link that also provides a range of about 10 m. Multiple data rates are defined for the LRP, with the lower data rates having near omni-directional coverage while the highest data rates are directional as shown in
The HRP and LRP operate in overlapping frequency bands and so they are coordinated in a TDMA (time division multiple access) manner by the MAC. The WVAN supports at least one uncompressed 1080p video stream with associated audio at a time. Multiple lower rate uncompressed video streams, e.g., two 1080i video streams, are also supported.
The WVAN supports two types of devices, coordinator and station. The coordinator controls the timing in the WVAN, keeps track of the members of the WVAN, transmits or receives data using the LRP or using the HRP. The station transmits and receives data using the LRP, initiates stream connections, and transmits or receives data using the HRP. The station may be capable of acting as a coordinator in the WVAN. Such a station is referred to as being coordinator capable.
In addition to the two MAC personalities of coordinator and station, each device in the WVAN will have one of four different PHY capabilities; HR0, HRRX, HRTX, and HRTR. HR0 is a device that is not able to either receive or transmit using the HRP. HRRX is a device that is able to receive in the HRP, but is not able to transmit using the HRP. HRTX is a device that is able to transmit in the HRP, but is not able to receive using the HRP. HRTR is a device that is able to both transmit and receive using the HRP.
All compliant wireless devices are able to transmit and receive using the LRP. Both the HRP and LRP may provide multiple data rates.
Detailed Operation of the Wireless Communication Systems
Some embodiments in a wireless high definition (HD) audio video (A/V) system will now be described. The A/V system may also include an audiovisual system.
The A/V stations 114 utilize a low-rate (LR) wireless channel 116 (dashed lines in
In one example, the device coordinator 112 is a receiver of video information (hereinafter “receiver 112”), and the station 114 is a transmitter of the video information (hereinafter “transmitter 114”). For example, the receiver 112 can be a sink of video and/or audio data implemented, such as, in an HDTV set in a home wireless network environment which is a type of WLAN. The transmitter 114 can be a source of uncompressed video or audio. Examples of the transmitter 114 include a set-top box, a DVD player or recorder, digital camera, camcorder, and so forth.
The application layer 210 of the transmitter 202 includes an A/V pre-processing module 211 and an audio video control (AV/C) module 212. The A/V pre-processing module 211 can perform pre-processing of the audio/video such as partitioning of uncompressed video. The AV/C module 212 provides a standard way to exchange A/V capability information. Before a connection begins, the AV/C module negotiates the A/V formats to be used, and when the need for the connection ended, AV/C commands are used to stop the connection.
In the transmitter 202, the PHY layer 206 includes a low-rate (LR) channel 203 and a high rate (HR) channel 205 that are used to communicate with the MAC layer 208 and with a radio frequency (RF) module 207. In certain embodiments, the MAC layer 208 can include a packetization module (not shown). The PHY/MAC layers of the transmitter 202 add PHY and MAC headers to packets and transmit the packets to the receiver 204 over the wireless channel 201.
In the wireless receiver 204, the PHY/MAC layers 214, 216 process the received packets. The PHY layer 214 includes a RF module 213 connected to the one or more antennas. A LR channel 215 and a HR channel 217 are used to communicate with the MAC layer 216 and with the RF module 213. The application layer 218 of the receiver 204 includes an A/V post-processing module 219 and an AV/C module 220. The module 219 can perform an inverse of the processing method of the module 211 to regenerate the uncompressed video, for example. The AV/C module 220 operates in a complementary way with the AV/C module 212 of the transmitter 202.
Cyclic Redundancy Checksum
A cyclic redundancy checksum (CRC) is a value which is computed from a block of data, such as a packet of data communicated via network communication. The checksum is used to detect errors after transmission. A CRC is computed and appended to the packet of data before transmission, and verified afterwards by the recipient to confirm that no changes occurred during the transmission.
In the wireless communication system having a transmitter and a receiver, the transmitter computes a cyclic redundancy checksum for a data packet which is being sent to the receiver and appends the checksum to the data packet. The receiver, receiving the data packet and the checksum, computes its own cyclic redundancy checksum for the received data packet, and compares the computed checksum with the received checksum to determine whether contents of the data packet changed during the transmission.
The data packet includes a payload to transmit, a PHY header, and a MAC header. The CRC is attached to the MAC header as a part of the data packet. Usually, the MAC header is variable in its size. It is inefficient to compute a CRC for a data packet of a variable size.
An aspect of the invention is to provide a MAC header of a fixed size or length. Since some fields of the MAC header could be of a variable length, a MAC header extension is used to handle the variable part of the MAC header. The variable part of the MAC header is isolated in the MAC header extension, and the length information or the size indication of the variable part is used in determining the CRC for the variable part of the MAC header.
More specifically, the non-extended portion, the MAC header, which is the portion of the data packet that is free from possibility of a variable size, is processed quite efficiently. In particular, computing the CRC for the PHY and MAC headers, both being of fixed lengths, is very efficient. For the MAC header extension which is of a variable length, a separate CRC is computed and the computation is facilitated by providing a size indication of the MAC header extension. The separate CRC computation enhances the reliability of the transmission of the MAC header extension in addition to maintaining the computing speed.
Generally, the source device uses a high rate link, which supports a multi-Gbps data rate for transmitting data to the destination device. This high rate link is shown in
There are two approaches in defining the HRP frame format for supporting data transfer: (1) using the existing audio video (A/V) frame format with some modification, and (2) using a new data frame format.
Use Existing A/V Frame Format with Modification
A few fields in an A/V frame format shown in
The PHY control field 711 comprises sub-fields for a beamtracking 713, a skewed constellation 714, a data or A/V indication 715, and a reserved space 716 as shown in
For data transfer, the freed fields, i.e., those fields that are no longer associated with a specific purpose and usable for data transfer include the video header (24 bytes) 104, the Clock Sync (6 bytes) 102, and two (6 bytes) of the sub-packet fields 106. The freed space may be used as a retransmit indicator field 855, which is added to the MAC header extension 850 as shown in
The retransmit indicator 855 may be formatted as shown in
Now referring to
Each of the plurality of payloads 861 may be formatted as in
Alternatively, a known sequence pattern may be added to the payload header to overcome the case of CRC error in the payload header such that the payloads can be extracted based on the known sequence pattern. This known sequence pattern may be similar to the pattern used in A-MPDU in IEEE 802.11n.
Use a New Data Frame Format
Referring to
Referring again to
The duration of each ACK group 771 can have a fixed duration if the PHY design has such limitation. For example, PHY may require each ACK group 772 to be 50 μsec long in one example. In this case, null data may need to be appended to the end of the last sub-packet in an ACK group 771 if sub-packets 772 from upper layer have variable sizes.
Each sub-packet 772 begins with an 8-bit delimiter 774, a 12 bit length information 775, a 4-bit CRC 776, and an MPDU 777. The MPDU 777 comprises a MAC header, the MAC header extension if there are security or link adaptation header information, and a MAC payload (MSDU or A-MSDU) information field. The Delimiter 774 may be set to a specific pattern, for example, ASCII code N as used in A-MPDU in IEEE 802.11n.
Referring to
The format of the MAC header 730 of
Compared to a MAC header for a HRP composite frame format for A/V applications in
In
One byte from the reserved 42 bytes 802 is used to indicate the retransmission status of each sub-packet. This one byte field is called as retransmission indicator 855 as shown in
In both of the new frame formats discussed above, there are a number of unused header bytes, which can be used as follows: since the A/V frame format of
Although embodiments of the invention have been described for use in a particular wireless HD video network, the HRP frame structure is not so limited. Embodiments can be used in general with other MAC protocols in wireless video network environment.
By using existing A/V frame format with modification of including a field to indicate that the packets do not contain audio video (A/V) data or using a new data frame format including a data packet indication field of the PHY control field as described above, the channel efficiency in a time insensitive data transfer such as file transfer in high data rate wireless networks can be significantly enhanced. The reduction in data transfer time results in a longer battery life in battery operated devices.
While the above detailed description has shown, described, and pointed out the fundamental novel features of the invention as applied to various embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the system illustrated may be made by those skilled in the art, without departing from the intent of the invention.
This application claims priority from U.S. Provisional Patent Application No. 60/872,948, filed on Dec. 4, 2006, which is incorporated herein by reference.
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