# Study Note 1
*by Griffani Megiyanto Rahmatullah (D11002813)*
*reference: [Random Access Procedure for 802.11be](https://patentimages.storage.googleapis.com/64/bd/50/789bf7a7271eec/GB2584885A.pdf)*

**Problem**
UORA is useful for wireless networks because it provides opportunities for the non-AP stations to transmit, without AP having polled them to know their needs for transmission. However, it suffers from various drawbacks. It suffers from a low maximum efficiency of 37% (successfully used random RUs) to be compared to 37% of unused random RUs and 26% of random RUs with collisions. The lost random RUs (either unused or collided) occur on large transmission durations (because transmitting non-AP stations have usually substantial amounts of data to transmit during UORA). This substantially decreases network efficiency.

The NDP Feedback Report procedure suffers from some limitations. For instance, it can address a limited set of (usually 18 or 36 for a 20 Mhz wide operating band) continous AIDs which may be punctured (some AIDs may not be assigned to non-AP stations or have been released when non-AP stations leave the AP during the lifetime of the network). The limited continous set of AIDs is not adapted to the gathering of feedback responses from a high number of non-AP stations, i.e. per BSS basis.

**Assumptions**
It is possible to obtain at once (i.e. using only one NFRP trigger frame) feedback report responses from stations of a larger group of stations than the range of scheduled AIDs implemented in the known NDP Feedback Report procedure. This is made possible by offering random access to the RU tone sets while targetting the NFRP trigger frame to larger groups of stations.

The random access by the stations is moved from the conventional basic trigger frame to the NFRP trigger frame. It advatageously reduces the impact of unused random resource units on netwrok efficiency because unused random resource units are lost for a shorter duration. The subsequent trigger frame assigns the RUs to specific stations that report they have a need (o.e. not random RUs), thereby aoiding unused resource units for longer durations as in the known techniques.

**System Architectures**
First figure schematically ilustrates a communication device of the radio network, etihter the AP or any non-AP STA, configured to implement at least one embodiment of the present invention. The communication device 400 may preferably be a device such as a micro-computer, a workstation or a light portable device. The communication device 400 comprises a communication bus 413 to which there are preferably connected:
- a central processing 411, such as microprocessor,denoted CPU
- a read only memory 407, denoted ROM
- a random-access memory 412, denoted RAM
- at least one communication interface 402 connected to the radio communication network over which digital data packets or frames or control frames are transmitted
Optional:
- a data storage 404 such as a hard disk
- a disk drive 405 for a disk 406, the disk drive being adapted to read data from the disk 406 or to write data onto said disk
- a screen 409 for displaying decoded data and/or serving as a graphical interface with the user, by means of a keyboard 410 or any other pointing means.
- may be optionally connected to various peripherals

Second figure is a block diagram schematically illustrating the architecture of the communication device 400 adapted to carry out, at least partially, the invention. As illustrated, communication device 400 comprises a physical (PHY) layer block 503, a MAC layer block 502, and an application layer block 501.

The PHY layer block 503 (e.g. a 802.11 standardized PHY layer) has the task of formatting, modulating on or demodulationg from any 20 MHz channel or the composite channel, and thus sending or receiving frames over the radio medium used 100, such as 802.11 frames, for instance single-user frames, such as control frames (e.g. ACK, Trigger Frame), MAC data and management frames, based on a 20 MHz width to interact with legacy 802.11 stations or with 802.11ax/be in legacy mode (such as Trigger Frames), as well as MAC data frames of OFDMA type having preferably smaller width than 20 MHz legacy (typically 2 or 5 MHZ), as well as NDP frames having preferably a PHY header transmitted on 20 MHz width and a short payload consisting on energy located on non-contiguous subcarriers or tones, to/from that radio medium.

The Mac layer block or controller 502 preferably comprises a MAC 802.11 layer 504 implementing conventional 802.11ax/be MAC operations, and additional block 505. Preferablym the additional block 505 referred to as NDP Feedback Management module 505 is configured to implement steps according to embodiment that are perfomed by the communication device 400, notably operations for a transmitting/responding station and receiving operations for a receiving station.

Interface 506 and 507 are used by the MAC and PHY layer block to interact and to exchange information through TXVECTOR (from the MAC to the PHY layer - 506) and the RXVECTOR (from the PHY to the MAC block - 507).

On top of Figure, application layer block 501 runs an application that generates and receives data packets. Application layer block 501 represents all the stack layers above MAC layer according to ISO standardization.

**Proposed Solution**

A Random Access mechanism for shor feedback procedure. An AP provides a random-access NFRP (null data packet, NDP, feedback report poll) trigger frame wherein a predefined Association Identifier, AID, value, e.g. 0 for to the plurality of RU tone sets and send an NDP feedback report response on the selected responding RU tone set. A dedicated backoff counter may be used for the purposes of contention to the random RU tone sets. A subsequent UL MU transmission can then be scheduled by the AP for the NDP responding stations. A subsequentr trigger frame may reserve RUs wherein RUs are assigned to the station based on the index of the Random Access RU selected for the response, possibly with an offset. No unused RU is expected, improving the random-access network efficiency. Also, the number of non-AP stations that can be targeted by the random-access NFRP trigger frame can be increased.

**Technical Terms**
16-bit Association IDentifiers (AIDs)
Access Point (AP)
Basic Service Set Identifier (BSSID)
BSRP Trigger Frame
BQRP Trigger Frame
Basic Trigger Frame
Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA)
Contention-based
Control Frame
Downlink (DL)
Feedback Report Poll (NFRP)
Multi User (MU)
Null-Data-Packet (NDP)
Orthogonal Frequency Division Multiple Access (OFDMA)
Resource Unit (RU)
Station (STA)
Trigger Frame
UL OFDMA-based random access (UORA)