CN1951070A - Multiple receiver aggregation(MRA) with different data rates for ieee 802.11n - Google Patents

Abstract

Method, frame definitions (300, 400, 500, 700, 800, 1000, 1200, 1300, 1400) and system for transmission of an aggregation of packets which includes a plurality of Medium Access Control (MAC) Protocol Units (MPDUs) or PLCP (Physical Layer Convergence Protocol) Protocol Data Units (PPDUs) intended for one or several receivers and transmitted at one or several different Physical (PHY) rates. In some aspects of the invention, a preamble, rsp.mid-amble (415.i, 515.i, 715.i, 815.i, 1015.i, 1215.i, 1315.i) is transmitted in-between each or between multiples of MPDUs or PPDUs allowing receiver devices to go into sleep mode and wake-up during the aggregate or packet burst. Furthermore, information is transmitted at the beginning of the aggregate/packet burst, which allows devices to deduce the position of MPDUs/PPDUs or multiples of MPDUs/PPDUs in the aggregate. MPDUs or PPDUs are grouped in order to enable efficient sleep times of the receiving devices. The receiving devices decode the information at the beginning of the aggregate/burst, fall into sleep-mode and wake up shortly before their packets have to be received.

Description

Multi-Receiver Aggregation (MRA) with different data rates for IEEE 802.11N

The present invention relates to apparatus and processes designed for use with a form of data transmission utilizing aggregated data frames having multiple packets. More specifically, the present invention relates to Multiple MCS (Modulation and Coding Scheme) and Receiver Aggregation (MMRA) data transmission and power saving.

Current wireless systems, such as LANs that operate under an access protocol known as IEEE 802.11, have several different options for modulation and coding in their physical layers. The choice of these options is usually determined by the maximum data rate, assuming the packet error rate is less than a given threshold.

For example, Task Group N of the current IEEE 802.11 specification is developing new physical (PHY) and medium access control (MAC) specifications for high data rate WLANs. Several industry groups are currently preparing proposals for Task Group N, including the industry association TGn Sync. The current specification of TGnSync does not consider different data rates in Multi-Receiver Aggregation (MRA). For example, the farthest receivers may typically have the slowest throughput, which may cause significant delays to other nodes/devices attempting to transmit or receive data, which in turn increases power consumption. In particular, if packets intended for different receivers are aggregated into one aggregate or burst and must be transmitted in the same MCS, some of these receivers experience a lower data rate than they can actually support. data rate, resulting in an inefficient use of the medium. The reason is that a single rate aggregate must be transmitted at a data rate that can still be decoded by the receiver with the worst radio link among all involved receivers. This data rate is usually much less than what a receiver with a better wireless link can still decode. These better radio links are therefore not optimally used by the single rate aggregation scheme.

Another problem with state-of-the-art packet aggregation schemes is that no power saving is possible during aggregation. Because aggregations can become very long, stations must stay awake for long periods of time, draining battery power. The reason why no power saving is possible is that the receivers either really don't know if they will receive packets during aggregation (and thus have to stay awake to check every packet in the aggregation), or because they know they will receive packets, but It is not known where in the aggregate the packet will arrive. Since during the receiver's sleep phase they will desynchronize to the time reference and to the channel state, even if the receivers know where their packets are in the aggregation, they cannot go into sleep mode before these packets start.

Therefore, there is a need in the art to provide packet aggregation that enables reception by different users at different PHY rates and that takes into account efficient power savings at the receiving station. However, this need has to be addressed with due consideration of Quality of Service (QoS) parameters including not only bandwidth (throughput), but also delay, delay jitter and packet loss rates as well as battery life.

Contents of the invention

The presently claimed invention provides a method, system and apparatus for providing a plurality of MAC protocol data units MPDUs to a group of different receivers. These MPDUs are either aggregated into a single PLCP (Physical Layer Convergence Protocol) Protocol Packet Data Unit (PPDU) or aggregated into a burst of PPDUs. This scheme supports the delivery of individual MPDUs at different PHY rates, with the potential to implement an efficient power saving scheme at the receiver device. A key feature of the invention is that, at the beginning of an aggregation, the identifier of the intended receiver of the aggregation (like for example the MAC address) and the position of the MPDU or PPDU within the aggregation is informed. Also, different MCS/data rates to transmit MPDUs or PPDUs are also notified. Another key feature is that a preamble or mid-sync is included between MPDUs in order to allow a receiving station to go into sleep mode and later rely on the pre/mid-sync to re-synchronize and eventually re-evaluate the channel.

Brief description of the drawings

Figure 1 shows a system with multiple devices and their different PHY transmission rates.

Fig. 2 shows a typical PPDU according to the prior art.

Figure 3 shows how a typical PPDU is changed according to the invention.

Fig. 4 shows a first variant of the aggregation information structure.

Fig. 5 shows a second variant of the aggregation information structure according to another aspect of the present invention.

FIG. 6 shows the active/sleep phases according to the first and second variants of the aggregation structures shown in FIGS. 4 and 5 .

Fig. 7 shows a third variant of the aggregation information structure according to another aspect of the present invention.

Fig. 8 shows a fourth variant of the aggregation information structure according to another aspect of the present invention.

FIG. 9 shows activity/sleep phases according to third and fourth variants of the aggregated information shown in FIGS. 7 and 8 .

Fig. 10 shows a fifth variation of the aggregation information structure according to another aspect of the present invention.

FIG. 11 shows activity/sleep phases according to a fifth variation of the aggregated information shown in FIG. 10 .

Fig. 12 shows a sixth variation of the aggregation information structure according to another aspect of the present invention.

Fig. 13 shows a seventh variation of the aggregation information structure according to another aspect of the present invention.

Fig. 14 shows an eighth variation of the aggregation information structure according to another aspect of the present invention.

FIG. 15 shows activity/sleep phases according to the seventh and eighth variants of the aggregated information shown in FIGS. 13 and 14 .

Fig. 16 shows a ninth variation of the aggregation information structure according to another aspect of the present invention.

FIG. 17 shows activity/sleep phases according to a ninth variation of the aggregated information shown in FIGS. 13 and 14 .

Figure 18 shows how the aggregate information structure is transmitted in a burst of MPDU or PPDU.

specific embodiment

Those of ordinary skill in the art will understand that the following description is provided for purposes of illustration and not limitation. A skilled artisan will appreciate that there are many variations within the spirit of the invention and scope of the appended claims. Unnecessary detail of known functions and operations may be omitted from the current description so as not to obscure the finer points of the invention.

FIG. 1A shows a typical example of a system for transmitting multi-rate aggregated packets according to the present invention. Furthermore, it is emphasized that a typical system will be much more complex than that shown and may include many different devices in communication either by wire or wirelessly. The system shown in FIG. 1A includes a plurality of nodes 112 , 113 , 114 and devices 115 . At least one of said plurality of nodes is adapted to receive a PPDU 125 comprising a packet aggregation according to the invention.

Also, one node 114 of the plurality of nodes 112, 113, 114 may have a different PHY transmission rate than the other nodes. It should also be noted that at least one (typically a plurality) of said plurality of nodes 112, 113, 114 is adapted to receive a superframe PPDU 125 comprising an aggregation of packets at different transmission rates 127, 128, 129. Thus, a series of different nodes with different transmission rates can use PPDUs according to the present invention at rates that maximize their efficiency.

Furthermore, it should be noted that at least one of the plurality of nodes 112, 113, 114 may comprise a legacy device 112 that transmits and receives non-aggregated packet frames according to a Medium Access Control (MAC) protocol.

One advantage of multi-rate aggregation according to the invention, compared to single-rate aggregation, is that all packets can be transmitted at the data rate that is optimal for each receiver and its quality of service requirements. For single rate aggregation and the scenario in Figure 1A, the entire packet would have to be transmitted at 6Mbps, since node 114 cannot receive data from individual senders at a higher data rate. For the present invention, the packets in Figure 1A can be transmitted at 6Mbps, 54Mbps and 108Mbps in the same aggregation.

Each node 112, 113, 114 within the WLAN 100 shown in FIG. 1A may comprise a system comprising the architecture shown in FIG. 1B. As shown, each node 112 , 113 , 114 may include an antenna 156 coupled to a receiver 152 that communicates over a wireless medium 160 . Each node 112 , 113 , 114 also includes a processor 153 and a PPDU processing module 154 . For example, in a node the processor 153 is configured to receive a frame comprising a PPDU from the receiver 152, and to process the PPDU using the PPDU processing module 154 to determine, for example, whether a packet is waiting to be transmitted to the node, and the processor 153 is arranged to is awake to receive these packets and store them in at least one buffer that is part of memory 158. The memory additionally stores information about the transmission type and number of packets to be received from each sender node. In the nodes 112 , 113 , 114 the processor 153 is also configured to use the PPDU processing module 154 to send aggregated/packet bursts.

Figure 2 shows the potential PPDU format for 802.11n as discussed by the TGn Sync Consortium. It should be noted that the PPDU format is chosen for illustrative purposes, and the invention is not limited to a specific PPDU format for TGn Sync. In FIG. 2, a traditional short training field (L-STF) 201, a traditional long training field (L-LTF) 202, and a traditional signal field (L-SIG) 203 are included for communicating with traditional 802.11 equipment. backward compatible. In the case of 40MHz transmission, these fields are transmitted using a bandwidth of 20MHz on two half-channels of the 40MHz channel, whereby the fields on one half of the bandwidth are phase rotated relative to the other half of the bandwidth. These legacy fields are followed by a High Throughput Signal field (HT-SIG) 204, which is also transmitted on two 20MHz channels in the case of 40MHz transmission. The subfields of HT-SIG are also shown in FIG. 2 . The HT-SIG 204 is important to the present invention because it is modified in most embodiments of the present invention to include multi-MCS and receiver aggregation information. After the HT-SIG, a High Throughput Short Training Field (HT-STF) 205 is transmitted (in 40MHz mode in case of 40MHz transmission) for automatic gain control (AGC) purposes. This field is followed by a number of High Throughput Long Training Fields (HT-LTF) 206, which are used for Multiple Input Multiple Output (MIMO) channel estimation and frequency or time synchronization. The number of HT-LTFs is equal to the number of antennas respectively transmitting streams. These different fields are not described in detail in this disclosure, but are only used as an example of what the structure of the PHY header might look like. The PHY header is followed by PSDU-DATA 207, which contains a Protocol Data Unit of the Media Access Control (MAC) layer called MPDU (MAC Protocol Data Unit).

FIG. 3 illustrates how Multiple MCS and Receiver Aggregation (MMRA) information may be included in the exemplary PPDU structure of FIG. 2 . The HT-SIG can be extended to include the MMRA part with all relevant MMRA information. The information in this MMRA section is one of the key features of the invention. However, the location of MMRA sections/information can be changed in accordance with the present invention. This is shown in some examples of the invention below. In Figure 3, the MMRA part is part of the PHY header of the PPDU. It can also be transmitted at the MAC level as an MPDU in the PSDU-DATA part of the PPDU. Another optional embodiment is that the MMRA part is transmitted as one single PPDU in case of a burst or aggregation of several PPDUs. In these latter two cases, the MMRA part in the PHY header will have zero length and accordingly will not be present.

In Figure 3, the HT-SIG also contains an additional bit to signal the MMRA type of data transmission. If the MMRA part is transmitted with a variable MCS (which may for example be the most robust (robust) MCS among all MCSs of the PSDU-DATA part of the PPDU), then the HT-SIG also contains the MMRA part as shown in Figure 3 MCS code. The MCS code does not have to be conveyed in an additional field of the HT-SIG since the existing RATE field can be used for this purpose.

Irrespective of whether the MMRA part is transmitted in the PHY header, MAC header as MPDU or as PPDU, it is necessary to transmit the MMRA part before the remaining PSDU-DATA part, ie each other PPDU. The reason is that, according to the invention, the MMRA part acts to allow for an effective power saving at the intended receiver as well as at all other receivers of the PPDU. It is also possible to place part of the MMRA information in the MMRA section within the PHY layer, and part of the information in the MAC layer, as will be shown in different aspects of the invention. These two different parts of the MMRA information will not represent the PHY part and the MAC part, but the MRAD of the MAC and the MMRA part of the HT-SIG of the PHY. MRAD stands for Multi Receiver Aggregation Descriptor and it is a term defined by TGn Sync. We reuse this noun for our purposes.

To allow this power saving scheme, the MMRA information includes the Station Identifier (STA-ID) of the intended receiver of the PPDU, and the position of the MPDU in the PSDU-DATA section in the case of a single PPDU, the individual PPDUs in the case of PPDU aggregation Location. By decoding the MMRA part, the receiver can deduce whether there is DATA for it in the PSDU-DATA part in the case of a single PPDU or in the individual following PPDUs in the case of PPDU aggregation . If a station is not mentioned as the intended receiver of the PPDU, it may go into sleep mode for the entire remaining PPDU. If a station is mentioned as intended receiver, the location information allows the receiver to deduce when it has to wake up during the PSDU-DATA section in the case of a single PPDU, and in the individual subsequent When it must wake up during the PPDU.

The location may be signaled by giving, for a particular receiver, the offset of the start of an MPDU or PPDU intended for that receiver relative to a predefined location. This predefined position may eg be the start of the (first) PPDU or the start of the PSDU-DATA section.

An optional way of signaling the location could be to include the length of the MPDU or PPDU intended for a particular receiver. This will give more detailed information to the receiver as it will know how much data to expect. On the other hand, a station will have to sum the lengths of all preceding length fields to arrive at the start of its MPDU or PPDU. Below we will always refer to length/offset to imply two possible ways of signaling position information.

In addition to the MMRA information, another key feature of the present invention is the inclusion of a preamble within the PSDU-DATA portion of the PPDU, which can therefore also be referred to as an intermediate sync. The purpose of the intermediate synchronization is to allow the receiver to re-synchronize with the PPDU and eventually also re-evaluate the channel after waking up from sleep mode during aggregation. This is required for the power saving scheme of the present invention, which allows receivers to go into sleep mode until the beginning of their MPDUs or the beginning of their MCS aggregation (see below: MCS aggregation is a group of MPDUs within a PPDU transmitted by the same MCS ).

In the case of PPDU aggregation no additional preamble is required since the PPDU is already started with a preamble. However, to save overhead, the PPDU preamble can be omitted for PPDUs within a PPDU aggregation. In this case, additional preambles/mid-syncs will again be required at locations within the aggregate where it should be possible for receivers to wake up.

There is a tradeoff between power saving efficiency and overhead due to intermediate synchronization. The more intermediate syncs inserted, the finer the granularity of possible wake-up points, and thus the more efficient the power saving scheme. On the other hand, the more intermediate synchronizations, the higher the overhead and the lower the data throughput. According to the invention, intermediate syncs are inserted either whenever the receiver changes, or whenever the rate/MCS changes. In most cases, several receivers' MPDUs or PPDUs will be transmitted with the same MCS. Therefore, inserting an intermediate sync every time the MCS changes results in fewer intermediate syncs per aggregation, but also results in less efficient power savings than by inserting an intermediate sync for each receiver. Including an intermediate synchronization whenever the MCS changes can be viewed as a tradeoff between power saving efficiency and overhead. With this solution, the scheme can also benefit PPDU aggregation, since the preamble of the PPDU can be omitted and only included in the PPDU aggregation whenever the MCS changes.

In some embodiments/aspects below, preambles/mid-syncs are inserted when the rate changes, while in other embodiments/aspects preambles/mid-syncs are inserted when the receiver changes. MPDU aggregation is shown in all figures because the usage of the scheme with PPDU aggregation will be similar, the MMRA part being transmitted in the first PPDU.

The structure of the preamble/midamble depends on whether the purpose is only a corresponding time and frequency adjustment, resynchronization, or whether a new channel estimate is also required. In the first case, the preamble only has to include a short training field, while in the latter case it also has to include a long training field. In the case of the standard IEEE 802.11n, this can result in a preamble in the range of 4us to 20us, depending on the purpose of the preamble/midamble.

Figure 4 shows the structure of the MMRA section 405 and PSDU-DATA 455 for an exemplary set of five devices in the context of the first aspect of the invention, two of which use modulation/coding scheme (MCS) 1 transmission, the other two are transmitted with MCS2, and the third is transmitted with a different MCS3. For simplicity, it is assumed in this example that each device sends only one MPDU. Multiple MPDU transmissions per device are obviously possible. The MMRA section begins with a length field 401 because the MMRA section can be of variable length. Also, according to this first aspect, for example the MMRA part belonging to the HT-SIG contains for each "j" of a device (STA) the following aggregated information:

● Receiver (STA) identifier (eg MAC address or association identifier) 402.j.1;

● MCS 402.j.2 of this MPDU; and

• PDU length or offset (given in number of bytes, symbols or time units) 402.j.3.

Such a set of three fields is called a "tuple" because it is a repeated grouping of the same fields, one tuple per MPDU. Each MPDU contains a MAC header and payload. The Receiver Address (RA) in the MAC header is the same MAC address as appears in the "STAID" field 402.j.1 of the MMRA section. The preamble 415.j following the MPDU is used by the receiving device to synchronize and demap the following MPDU 425.j at the desired data rate (indicated in the MCS field of the MMRA section).

With this first aspect of the invention, there are multiple tuples that can contain the same STA ID. Multiple tuples with the same STA ID result in a particular device receiving multiple MPDUs within this aggregated PSDU. MPDUs destined for one device can further be arranged next to each other in order to improve power saving at the receiver.

As shown in FIG. 5, the second aspect of the invention differs from the first aspect of the invention with respect to the functionality of tuples. In a third aspect, a tuple in the MMRA section may refer to multiple MPDUs for the same target device. Included in the tuple is an additional field 502.i.2 indicating the number of MPDUs for each target device. Individual fragments of MPDUs and tuples may or may not be of the same size, since the length field indicates the total length of all MPDUs for this target device. If an offset is used instead of the length of the MPDU, then the start or end of all MPDUs destined for a certain receiver is signaled. The offset can be defined in units of bytes, symbols or time respectively.

Regarding the above-mentioned fields of the first and second aspects of the present invention, these fields are enough for one STA to calculate when it should start receiving data and for how long. One advantage of the present invention is that a STA can decide to implement a power saving scheme when it does not have to receive any data.

Figure 6 shows the sleep-wake cycles at the five devices (STA1 to STA6) used as examples in Figures 4 and 5 to illustrate the first aspect of the present invention during reception of a typical aggregated PPDU with different receivers. and the second aspect, and shows the sleep mode of the sixth device STA6, which is not mentioned as receiver in the PPDU. This STA6 can stay in sleep mode during the whole frame transmission because the MMRA part contains the STA identifier of the receiving STA of this PPDU. It can be seen that STA6 remains at a low level (indicating sleep) throughout the PPDU.

Advantages of the first and second aspects include:

1. No interframe space (IFS) and backoff between MPDUs with different MCS (IFS may have to be included if transmit power changes during aggregation);

2. Effective power saving of STA;

3. The STA knows that it can receive the MPDU in this aggregated PPDU;

4. MPDUs can be delivered to each STA at different PHY rates;

5. Efficient use of the medium; and

6. No MPDU delimiter is required.

Disadvantages of the second aspect include:

1. The PHY needs to have knowledge about the MAC address of the device (if the MMRA part is transmitted as part of the HT SIG in the PHY header);

2. The PHY needs to know the MPDU boundary, because aggregation is no longer a pure MAC function;

as well as

3. As many preambles/midambles are required as there are MPDUs.

In FIG. 7, an example including a frame format for the MMRA part and PSDU-DATA of the third aspect of the present invention is shown. Similar to the previous example, five devices are shown, two of which transmit with MCS1, the other two transmit with MCS2, and the third transmit with a different MCS3. One difference that distinguishes this third aspect of the invention from eg the second aspect of the invention is that MPDUs using the same MCS are grouped. In addition to the total length of the MMRA section 701, the following aggregation information is included in the MMRA section for each group of receiving STAs with the same MCS:

- MCS 702.i.1 for a group of STAs with the same MCS (MCS aggregation);

- Length or offset 702.i.2 of all aggregates with the same MCS;

Number of receivers (indicates how large the next subfield containing the device's STA identifier is) 702.i.3; and

• STA Identifier List 702.i.j, j≥0.

Similar to the previously illustrated example, the PSDU contains all the MPDUs (MAC header + payload) and appends them with an MPDU_Delimiter (length and CRC) in order to delimit the MPDU and optionally also indicate the next The length of the MPDU. The MPDU delimiter may, for example, contain the length of the following MPDU, a cyclic redundancy check (CRC) and a unique pattern (not shown).

In contrast to the previously shown aspects of the invention, in the third aspect preambles/mid-syncs are only used to separate aggregates of different MCSs. It should be noted that in all mentioned aspects of the invention an interframe space (IFS) may be inserted before the preamble/midamble. If the transmission power within the aggregate is changed, interframe spacing may be required, for example. Two MPDUs of the same rate will be separated using only one MPDU_Delimiter, however the next MPDU at a different rate will be preceded by a preamble/intermediate sync for synchronization after the sleep-wake phase and eventually for channel estimation the goal of. The use of PDU delimiters between MPDUs of the same rate is not necessarily required, but can be considered as an option. The preamble following the aggregation of MPDUs (with the same MCS) can be used by the receiving device to synchronize and demap subsequent MPDUs at the desired data rate (indicated in the MCS field of the MMRA section).

Figure 8 shows the MMRA part and PSDU-DATA frame format of the fourth aspect of the present invention, which uses the previous example of five stations, two of which transmit with MCS1, and the other two transmit with MCS2, and The third one is transmitted with a different MCS3. The difference from the third aspect of the invention is that in the fourth aspect the length or offset is not given per MCS aggregation but in a more specific per receiving station manner . As in the third aspect, preambles/mid-syncs are included whenever the MCS changes.

Fig. 9 shows the sleep-wake cycle at five stations (STA1-STA5) during reception of a typical aggregated PPDU according to the third and fourth aspects of the present invention, and the sleep mode of STA6, which is not used as the receiver machine listed. Since the MMRA part contains the STA identifier of the receiving STA of this PPDU, this STA6 can remain in sleep mode during the entire frame transmission. A station listed as a receiver in the MMRA section may enter sleep mode until the start of its MCS aggregation. An MCS aggregation is a group of MPDUs transmitted by the same MCS. This can mean that a station has to wake up sometime before its own MPDUs are received. However, this is required because the station must wake up before the preamble/mid-sync in front of its MCS aggregation.

Advantages of the third and fourth aspects include:

1. No IFS (in case of constant power) and no compensation between MSDUs with different MCS;

2. Effective power saving of STA;

3. The STA knows that it can receive the MPDU in this PPDU;

4. MPDUs can be delivered to each STA at different PHY rates;

5. Efficient use of the medium; and

6. A smaller number of preambles/midambles is required to separate MPDUs with different data rates.

Disadvantages of the third aspect include:

1. The PHY needs to have knowledge about the MAC address of the device (if the MMRA part is transmitted as part of the HT SIG in the PHY header);

2. The PHY needs to know the boundaries of aggregation of different data rates, because aggregation is no longer a pure MAC function;

3. Requires as many pre-syncs/inter-syncs as there are MCS aggregates; and

4. Lower power saving efficiency than the first and second aspects.

In the case of the first four aspects of the present invention, the MMRA section contains the entire MMRA information and is included either as part of the PHY header in the case of a single PPDU, or in a separate PHY header in the case of a PPDU burst. within the PPDU. However, MMRA information can also be split between the PHY and MAC layers, as mentioned earlier. Fig. 10 shows the MMRA part and PSDU-IDATA frame format of the fifth aspect of the present invention, where MMRA information is split between PHY and MAC layers. Let us again use the previous example of five devices, two of which transmit with MCS1, the other two transmit with MCS2, and the third transmit with a different MCS3. In this case, the MMRA part which is part of the HT-SIG in the PHY layer, besides its own total length 1001, contains only such information as is required by the PHY layer in order to decode the packet, which for each MCS aggregation "i" is:

- MCS 1002.i.1 for the group of STAs with the same MCS (MCS aggregation);

as well as

• The length or offset 1002.i.2 of the MCS aggregate "i".

As shown in Figure 10, the detailed information about the receiver is not included in the MMRA part, but in the PSDU-DATA in the attached MPDU, which is called MRAD (Multiple Receiver Aggregation Description) according to the nomenclature of the TG Sync specification symbol). This MPDU contains STA IDs, such as the MAC addresses (or compressed versions) of all stations whose MPDUs are included in the subsequent MCS aggregation. The Basic Service Set Identifier (BSS-ID) may also be included in the MRAD if a short STA ID is used, such as an Association Identifier. Similar to the third and fourth aspects of the invention, preambles/midambles are used to separate aggregations of different MCSs.

Optionally, the MRAD may also contain the number of MPDUs for this MAC address and/or the length or offset of all MPDUs intended for the respective receiver. This latter optional information is useful in order for the intended receivers to wake up only when their own MPDUs are transmitted. There are as many MRAD MPDUs as there are MCS groups.

Figure 11 shows the sleep-wake cycle at five devices (STA1-STA5) during reception of a typical aggregated PPDU, and the sleep mode of STA6, which is not listed as a receiver, according to a fifth aspect of the invention . In contrast to the aspect of the invention discussed above, STA6 must wake up at the beginning of each MCS aggregation 1101, synchronize with the preamble/midamble and decode the MRAD MPDU in order to check whether its ID is mentioned as a receiver . Only when the STA is not listed as a receiver can it go back to sleep mode.

Advantages of the fifth aspect include:

1. No IFS (in case of constant power) and no compensation between MSDUs with different MCS;

2. Effective power saving of STA;

3. The STA knows that it can receive the MPDU in this super PPDU;

4. MSDUs can be delivered to each STA at different PHY rates;

5. Effective use of media;

6. A smaller number of preambles/intermediates are required to separate MPDUs with different data rates;

7. Not all MAC addresses in HT-SIG2 need to be sent; and

8. Less PHY overhead.

Disadvantages of the third aspect include:

1. The PHY needs to know the boundaries of aggregation of different data rates, because aggregation is no longer a pure MAC function;

2. Require as many pre-syncs/inter-syncs as there are aggregations;

3. Lower power saving efficiency than the first and second aspects; and

4. Power saving is not optimal for devices not involved in the aggregation.

Figure 12 shows a modification of the above aspect of the invention. In the sixth aspect of the present invention, the detailed information about the receiver is again contained in the MMRA part, while the PSDU-DATA frame format of the fifth aspect of the present invention is retained. In this way, the sixth aspect of the invention has exactly the same sleep-wake cycle as in Fig. 11, but STA6, which is not listed as a receiver, can remain in sleep mode during the entire frame transmission because the MMRA section contains this STA identifier of the receiving STA of the PSDU.

Figure 13 depicts a seventh aspect of this aspect, which differs from the fifth aspect in Figure 10 in that the MRAD information is not included in the first few MRADs of each MCS aggregation, but is instead included in Merged into Ultra MRAD 1309. This super MRAD may eg be a single MPDU or PPDU containing the number of receivers 1309.1 of the aggregate and the STA identifier (like MAC address for example) 1309.2 of each station whose MPDU or PPDU is included in the aggregate. Optionally, the MRAD may also contain the length or offset 1309.3 of all MPDUs or PPDUs intended for the respective address. This information is useful to allow intended receivers to wake up only at the beginning of the sub-aggregation in which their own MPDU or PPDU is transmitted. For this purpose, presync/midsync are again used to separate aggregations of different MCSs.

FIG. 14 shows the eighth aspect of the present invention, in which the Super MRAD includes not only the STA identifier together with the offset or length of each MPDU or PPDU, but also information on the modulation and coding scheme (MCS). This aspect can be seen as an extreme solution, where all information is included on the MAC level, and the opposite of this solution, where all information is included in the PHY header.

Figure 15 shows the sleep-wake cycle at five stations (STA1-STA5) during reception of a typical aggregated PSDU according to the seventh and eighth aspects of the present invention, and the sleep mode of STA6, which is not part of the receiving machine listed. These two solutions solve the problem arising in the fifth aspect of the invention that STA6 has to wake up at the beginning of each MCS aggregation. In this case, STA6 can enter sleep mode for the remaining PPDUs following the super MRAD, since the super MRAD contains the STA identifier of the receiving STA of this PPDU.

In Figure 16, the MMRA part and PSDU DATA frame format are shown to illustrate the ninth aspect of the invention, which uses the previously allocated number of five stations, two of which transmit with MCS1 and the other two with MCS2 for transmission, and a third with a different MCS3 for transmission.

• Detailed information about the receiver is contained in the PSDU-DATA within the additional Ultra MRAD MPDU 1609. This Ultra MRAD MPDU contains:

The number of receivers 1609.1;

The MAC address of the receiver of this MCS 1609.2; and

• After each receiver MAC address: length or offset 1609.3 of the MPDU for each receiver.

In contrast to the previously exemplified aspects of the invention, neither MPDUs nor MCS aggregates are separated by preambles. Depending on hardware capabilities, two different situations can arise: either the MPDU delimiter is sufficient for synchronizing with the MCS aggregate after waking up, or there may be no sleep during the entire PPDU. To provide the necessary length information to those devices capable of utilizing it, for each MCS "i" the MCS and length or offset may be included in the MMRA section:

● MCS 1602.i.1 of a group of STAs with the same MCS (MCS aggregation)

● Length or offset of each MCS aggregate 1602.i.2

If this information is not included in the MMRA part, then the super-MRAD MPDU must include the MCS code, and must include as many super-MRADs as there are different MCS in the PPDU. However, it is assumed here that this information is included in the MMRA part field.

Figure 17 shows the sleep-wake cycle at five stations (STA1-STA5) during reception of a typical aggregated PPDU, and the sleep mode of STA6, which is not listed as a receiver, according to the ninth aspect of the invention . In this figure, it is assumed that the MPDU delimiter is sufficient for synchronizing with the MCS aggregate after waking up. However, for the ninth aspect, due to the lack of preambles/mid-syncs, there is likely no resynchronization and no power saving.

Various modifications can be made to the invention without departing from the spirit of the invention and the scope of the appended claims. For example, a superframe with multiple aggregated packets may have different header arrangements than those shown, as desired or preferred. Aggregation information may be included at the physical layer level (in the PHY header) or at the MAC layer level (eg in a separate MPDU) or within a separate PPDU. Both MPDU and PPDU aggregation are also possible with the present invention. Any variations of the aspects described are therefore within the spirit of the invention. The system can use many different types of nodes, and the transmission can be wired or wireless. Protocols other than 802.11 may also be used as long as they are suitable to accept packet aggregation.

Figure 18 shows how the above embodiment has to be interpreted if the different MPDUs are not sent within a single PPDU but eg as a burst of multiple MPDUs or PPDUs. The basic idea still applies. Each PPDU has its own preamble, however to save overhead this can be changed in some embodiments to only include preambles between PPDUs of different MCSs. In Fig. 19 some parts of the PPDU like eg the PLCP header are not explicitly shown in order to be able to use the same diagram to illustrate the aggregation of MPDUs or PPDU bursts. It is also shown in Fig. 18 that interframe spaces can be inserted within an aggregation/burst without changing the basic structure of the embodiment. Interframe spaces may be inserted, for example, in case of a change in power level. Finally, it is emphasized that the aggregation scheme of the present invention can be applied to segmented or non-segmented MAC Service Data Units (MSDUs).

While a preferred embodiment of the present invention has been shown and described, those skilled in the art will appreciate that the device architecture and methods described herein are illustrative It is intended that various changes and modifications may be made and equivalents may be substituted for parts thereof without departing from the true scope of the present invention. In addition, various modifications may be made to adapt the teachings of the invention to a particular situation without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (41)

1. A method of aggregate transmission of a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) (425i), comprising the steps of: aggregating the plurality of MPDUs into one aggregation/packet burst; The aggregation/packet burst is formatted by performing the following sub-steps: a. correspondingly including at least one of a preamble, an intermediate sync (415.i) in the middle of an MPDU of said plurality of MPDUs and in at least one of a set of multi-MPDUs of said plurality of MPDUs, and b. including information comprising data at the beginning of the aggregation/packet burst to allow at least one receiver device to deduce the position of the at least one MPDU and the set of multiple MPDUs within the aggregation/packet burst; transmitting the formatted aggregate/packet burst to at least one receiver device or one of a group of receiver devices using at least one physical (PHY) rate; and At least one receiver device or at least a group of receiver devices enters sleep mode and wakes up during aggregation/packetization bursts. 2. The method of claim 1, wherein the formatting step further comprises the following substeps: a. Formatting said MPDU 425.i within a single PLCP (Physical Layer Convergence Protocol) Protocol Packet Data Unit (PPDU) (400). 3. The method of claim 1, wherein the formatting step further comprises the following substeps: a. Formatting said MPDUs within a plurality of PLCP (Physical Layer Convergence Protocol) Protocol Data Units (PPDUs) such that at least one MPDU per PPDU (215) acts as a burst or aggregation of PPDUs. 4. The method of claim 1, wherein the formatting step further comprises the following substeps: a. Formatting information within a single MPDU 425.1 preceding said plurality of MDPUs. 5. The method of claim 2, wherein the formatting step further comprises the following substeps: a. Format the information of a separate MPDU within the Media Access Control (MAC) header of the PPDU, or within the PPDU. 6. The method of claim 2, wherein the formatting step further comprises the following substeps: a. Format the information within the PHY header of the PPDU. 7. The method of claim 2, wherein the formatting step further comprises the following substeps: a. Formatting a portion of the information within the PHY header and the remainder of the information within one of the MAC header or a separate MPDU within the PPDU. 8. The method of claim 2, wherein the formatting step further comprises the following substeps: a. Include at least one bit (308) that identifies the PPDU as containing an aggregation of packets. 9. The method of claim 1, wherein for each of the at least one receiver device or a group of receiver devices, the information further includes at least: an identifier of said at least one receiver device or group of receiver devices (402.i.1); Modulation and coding scheme (MCS) of at least one of a particular MPDU or a set of MPDUs or PPDUs (402.i.2); and Length or offset (402.i.3) of at least one PPDU or group of PPDUs. 10. The method of claim 9, wherein said information further includes a Basic Service Set ID (BSSID). 11. The method of claim 9, wherein said identifier is a MAC address. 12. The method of claim 9, wherein the information further includes at least one of a plurality of MPDUs and a plurality of PPDUs for the same receiver. 13. The method of claim 9, wherein said information further includes at least one group selected from the group consisting of a plurality of MPDUs and a plurality of PPDUs, and further comprising the step of transmitting said at least one group with the same MCS. 14. The method of claim 1, wherein comprising substep a. further comprising the following substeps: a.1 Include said preamble, midamble (415.i) accordingly between MPDUs (425.i) intended for different receivers. 15. The method of claim 1, wherein comprising substep a. further comprising the following substeps: a.1 Include said preamble, interamble (715.i) accordingly between groups of MPDUs (756) transmitted with different MCSs (702.i.1). 16. The method of claim 1, wherein the comprising substep a. further comprising the following substeps: a.1 includes said preamble, midamble and an interframe space accordingly between groups of MPDUs transmitted at different power levels. 17. The method of claim 1, further comprising the step of at least one receiver of the aggregate sending a response frame upon receipt of the aggregate. 18. The method of claim 17, wherein the sending step further comprises the step of the at least one receiver sending response frames in an order scheduled by the aggregated sender. 19. The method of claim 3, further comprising the step of at least one receiver interrupting said aggregation/burst and thereafter sending a response frame. 20. The method of claim 2, wherein the formatting step further comprises the step of formatting the PPDU to include: One of a High Throughput Signal field (HT-SIG) (304) and a separate PPDU with a MMRA (304.2) (405) part comprising at least one tuple (402.i.1- 3) the total length (401); and At least one tuple (402.i.1-3) comprising the following aggregated information for each of a plurality of respective receiver devices: i. an identifier (402.i.1) of each respective receiver device, ii. MCS (402.i.2) at which to transmit at least one MPDU (425.i) or set of MPDUs to each respective receiver device, and iii. Length or offset of at least one MPDU or set of MPDUs to the respective receiver device (402.i.3). 21. The method of claim 2, wherein the formatting step further comprises the step of formatting the PPDU to include: One of a High Throughput Signal field (HT-SIG) (304) and a separate PPDU with a MMRA (304.2) (505) part comprising at least one tuple (502.i.1- 4) the total length (501); and At least one tuple (502.i.1-4) comprising the following aggregated information for each of a plurality of respective receiver devices: i. an identifier (502.i.1) of each respective receiver device, ii. Number of receivers (502.i.2), comprising at least one of an MPDU or a set of MPDUs destined for each respective receiver device, iii. MCS (502.i.3) with which to transmit at least one MPDU or set of MPDUs destined for each respective receiver device, and iv. Length or offset of at least one MPDU or set of MPDUs destined for the respective receiver device (502.i.4). 22. The method of claim 2, wherein the formatting step further comprises the step of: a. Format the PPDU to include: (1) One of a High Throughput Signal field (HT-SIG) (304) and a separate PPDU with a MMRA (705) section comprising at least one tuple following (702.i.1- 5) the total length (701); and (2) At least one tuple (702.i.1-5) that includes the following aggregated information for at least one receiver device and one of at least one set of receiver devices, wherein the at least one set of receiver devices includes Multiple receiver devices for which at least one MPDU is transmitted with the same MCS: i. MCS (702.i.1) for at least one receiver device and at least one of at least one of a plurality of receiver devices having the same MCS (MCS aggregation), ii. the length or offset (702.i.2) of the at least one MPDU with the same MCS, iii. A number N of receivers (702.i.4), comprising at least one of said at least one receiver device and at least one of at least one plurality of receiver devices for which packets are sent with a respective MCS, and iv. N receiver address lists (702.i.4-N), containing at least one of the addresses of said at least one receiver device and at least one set of addresses for which packets are sent with the respective MCS . 23. The method of claim 2, wherein the formatting step further comprises the step of: a. Format the PPDU to include: (1) One of a High Throughput Signal field (HT-SIG) (304) and a separate PPDU with a MMRA (805) section comprising at least one tuple (802.i.1- N) total length (801); and (2) At least one tuple (802.i.1-N) comprising the following aggregated information for at least one receiver device and at least one of a plurality of receiver devices, where the same MCS is the at least one group Multiple receiver devices transmit at least one MPDU: i. MCS (802.i.1) for at least one receiver device and a group of multiple receiver devices with the same MCS (MCS aggregation), ii. Number of receivers N (802.i.2), comprising at least one of said at least one receiver device and at least one of at least one plurality of receiver devices for which packets are sent with respective MCSs, and iii. N receiver address lists (802.i.3-N) containing at least one of the addresses of the at least one receiver device and at least one of a plurality of receiver devices for which packets are sent with the respective MCS , each entry includes a receiver address and the length or offset of at least one MPDU intended for that receiver. 24. The method of claim 2, wherein the formatting step further comprises the step of: a. One of a separate PPDU comprising a High Throughput Signal field (HT-SIG) (304) and having a MMRA part (1005) comprising at least one tuple following (1002.i.1- 2) The total length (1001), and for each group of multiple receiver devices (MCS aggregation) of MPDUs transmitted with the same MCS includes a tuple consisting of: i. The MCS of the set of multiple receiver devices (1002.i.1); and ii. The length or offset of all MPDUs scheduled for the group (1002.i.2). 25. The method of claim 24, wherein the formatting step further comprises the step of: a. Include a Multi-Receiver Aggregation Descriptor (MRAD) (1008.1), either as part of the first MAC header in the PPDU or as a separate MPDU in the data portion of the PPDU. 26. The method of claim 2, wherein the formatting step further comprises the step of: a. Include a Multi-Receiver Aggregation Descriptor (MRAD) (1208.1), either as part of the first MAC header in the PPDU or as a separate MPDU in the data portion of the PPDU; and b. Include aggregated information including a device identifier (1201.i.4-...) for each of a plurality of receiver devices having at least one receiver device with a different modulation/coding scheme (MCS) for transmission. 27. The method of claim 3, wherein the formatting step further comprises the step of: a. Include the Multi-Receiver Aggregation Descriptor (MRAD) (1208.1) as a separate PPDU at the beginning of the burst/aggregation; and b. Include aggregated information including a device identifier (1201.i.4-...) for each of a plurality of respective receiver devices having at least one receiver device with a different modulation/coding scheme ( MCS) for transmission. 28. The method of claim 1, wherein the formatting step further comprises the step of: a. Include some or all of this information as part of the aggregation/burst in a Super Multi-Receiver Aggregation Descriptor (MRAD) (1309), the MRAD including one of its own MPDU and PPDU, the information also including : i. Number of receivers N (1309.1); and ii. For each receiver, include: (a) device identifier (1309.2.1-N), and (b) One of the length or offset of the MPDU intended for the receiver (1309.3.1-N). 29. The method of claim 1, wherein the formatting step further comprises the step of: a. Include at least some of said information as part of the aggregation/burst in a Super Multi-Receiver Aggregation Descriptor (MRAD) (1409), said MRAD including one of its own MPDU and PPDU, said information being relevant to the same Each set of MPDUs or PPDUs transmitted by the MCS also includes information selected from the following groups: i. MCS (1402.i.1) of each group of MDPU or PPDU; ii. the number N of receivers within the set of MDPUs or PPDUs; and iii. For each receiver in the set of MDPUs or PPDUs (1402.i.2): the device identifier and the length or offset of the MPDU intended for the respective receiver. 30. The method of claim 1, wherein the step of entering sleep mode further comprises the step of the aggregated at least one receiver device or at least one group of receiver devices performing the step of: deducing from the included information the start of a plurality of MPDUs intended for the at least one receiver device or at least a group of receiver devices; and Going into sleep mode and accordingly waking up before the most recent pre-intermediate synchronization that was executed before the start of a plurality of MPDUs intended for the at least one receiver device or at least one group of receiver devices send. 31. A system for multi-rate packet aggregation comprising: a plurality of nodes 112, 113, 114; a device 115; Wherein at least one node of the plurality of nodes is adapted to receive a PPDU comprising a multi-rate packet aggregation or a multi-rate packet burst. 32. The system of claim 31, wherein one node 114 of said plurality of nodes 112, 113, 114 has a different PHY transmission rate. 33. The system of claim 32, wherein a plurality of nodes of said plurality of nodes 112, 113, 114 are adapted to receive PPDUs comprising packet aggregations or packet bursts with different transmission rates 127, 128, 129. 34. The system of claim 32, wherein the permutations of aggregated packets are grouped to provide power savings to the plurality of nodes for transmitting and receiving superframes. 35. The system of claim 32, wherein said plurality of nodes comprises devices (112, 113, 114) and access points (115) operating under IEEE 802.11 adapted to send/receive superframes comprising a plurality of packets or Packet burst. 36. The system of claim 31, wherein: Preambles, mid-syncs are transmitted in the middle of each MPDU or between MPDUs accordingly to allow receiving devices to enter sleep mode and wake up during aggregation; Information is conveyed at the beginning of an aggregation that allows a device to infer the position of the MPDU or MPDUs within the aggregation. 37. The system of claim 36, wherein a receiver of the aggregate deduces from said information in the aggregate the start of the MPDU intended for it, enters sleep mode and correspondingly transmits the most recent MPDU before the start of its MPDU Wake up before and during sync. 38. The system of claim 37, wherein the pre- and inter-synchronization are respectively used to re-synchronize and re-estimate the channel on the physical layer when waking up from the sleep mode, respectively. 39. An apparatus for managing aggregated transmission of multiple media access control (MAC) protocol data unit (MPDU) packets, comprising: An antenna (157) for sending and receiving aggregated/packet bursts; a receiver (152), coupled to the antenna (157) to receive aggregated/packet bursts (1800) transmitted over the wireless medium (160); A transmitter (156), coupled to an antenna (157) to transmit aggregated/packeted bursts (1800) over a wireless medium (160) using at least one physical (PHY) rate to a receiver selected from at least one receiver or at least a group of multiple receivers receivers in said group of machines; PPDU processing module (154) for processing transmitted and received aggregation/packet bursts (1800) to respectively locate or deduce the position of at least one of said plurality of MPDUs therein; A processor (153), coupled to said receiver, transmitter, and PPDU processing module, is used to aggregate data into and decompose data from aggregation/packet bursts respectively, said aggregate/packet burst sending at least one of the plurality of MPDUs comprising: i. at least one of a preamble, an intermediate sync (415.i) in between groups of at least one of said plurality of MPDUs, and ii. information at the beginning of an aggregation/packet burst that allows at least one receiver or at least one group of receivers to deduce the location of at least one of the plurality of MPDUs; Wherein said at least one receiver or at least a group of receivers enters a sleep mode and wakes up during aggregation/packetization bursts. 40. The device of claim 39, wherein the PPDU processing module is further configured to format said MPDU within a single PLCP (Physical Layer Convergence Protocol) Protocol Packet Data Unit (PPDU). 41. The device of claim 39, wherein: The PPDU processing module is further configured to make at least one MPDU per PPDU as an aggregation/packet burst by formatting said MPDUs within a plurality of PLCP (Physical Layer Convergence Protocol) Protocol Data Units (PPDUs); And the processing unit is also configured to address aggregate/packet bursts to one or several receivers, and direct the transmitter 156 to transmit aggregate/packet bursts at one or several different physical (PHY) rates.

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