How IEEE 8011 Works?

Step 1: Data Frame Preparation:

When a station wants to transmit data, it creates a MAC Service Data Unit (MSDU). This is essentially the raw data the station wishes to send. To ensure successful transmission and proper communication, the station adds specific headers to the MSDU. With these headers added, the data unit is now termed a MAC Protocol Data Unit (MPDU).

Step 2: Wait Before Transmission:

Before rushing to transmit the MPDU, the station first waits for a time duration called DCF Interframe Space (DIFS). This is a predetermined time that ensures the medium is not accessed immediately and reduces the chances of collision.

Step 3: Channel Assessment:

Using the CSMA/CA protocol, the station checks if the transmission medium (typically air in the case of Wi-Fi) is currently being used. If the channel is detected as busy, the station doesn’t transmit immediately and moves to the back-off procedure. If it’s idle, it proceeds to transmit.

Step 4: Back-off Procedure:

Instead of all stations trying again immediately after the medium becomes free, each station chooses a random time period from the Contention Window (CW) to wait. This randomness reduces the chance of collisions when multiple stations want to transmit. After the back-off time elapses, the station senses the medium again to check if it’s free.

Step 5: Data Transmission:

If after the back-off (or immediately after DIFS if the channel was initially free), the channel is sensed as idle, the station transmits its MPDU.

Step 6: Acknowledgement Process:

Once the receiving station gets the MPDU and determines it’s for them and that it’s error-free, it waits for a short duration called Short Interframe Space (SIFS) before acknowledging. Post-SIFS, the receiving station sends an ACK frame to the sender, signaling the successful reception of the MPDU.

Step 7: Successful Transmission:

The sending station, upon receiving the ACK frame, knows that its data has been successfully transmitted and received. This marks the end of the current DCF cycle for that data unit.

Limitations

During the entire procedure, the transmission time is divided into a DCF Interframe Space (DIFS), a Contention Window back-off time, the Physical Layer Protocol Data Unit (PPDU) transmission time, a Short Interframe Space (SIFS) and the ACK frame transmission time. The overhead and waiting time involved in this mechanism results in the inefficiency of the channel utilization and limited data throughput.

IEEE 802.11 Architecture, more popularly known as WiFi is widely used to provide anywhere-anytime networking access. New enhancements keep getting introduced as global connectivity demands evolution and improvement. The IEEE 802.11 amendment was introduced to enhance the traditional 802.11 for higher throughput and improve wireless technologies.

The primary objective of this amendment is to bolster the MAC (Medium Access Control) layer’s Quality of Service (QoS). By refining QoS, the IEEE aspires to cater more efficiently to the escalating demands for bandwidth. This is increasingly crucial in an era where high-definition streaming, online gaming, remote work, and the proliferation of Internet of Things (IoT) devices are driving unprecedented levels of data traffic.

In this article, we will delve deeper into the enhancements introduced in this amendment. This will encompass improvements in both the physical layer communications design and the MAC layer. We will discuss how these enhancements not only facilitate higher throughput but also offer a more resilient and efficient wireless communication system.