PSMP Power Save Multipoll

Power Save Multipoll (PSMP) is a mechanism designed to optimize power consumption in wireless communication networks, specifically in the context of the IEEE 802.11 standard, which governs Wi-Fi networks. It is an enhancement to the Power Save Mode (PSM) mechanism and aims to reduce energy consumption by enabling more efficient polling of stations (STAs) in a Wi-Fi network.

In a typical Wi-Fi network, there is a central access point (AP) that coordinates communication with multiple STAs. The AP periodically polls the STAs to check if they have any data to transmit. The PSM mechanism allows STAs to conserve power by specifying specific intervals during which they can sleep and wake up only when the AP polls them. However, this can introduce inefficiencies when there are multiple STAs with varying traffic patterns.

PSMP addresses these inefficiencies by allowing the AP to simultaneously poll multiple STAs in a single transmission, thus reducing the number of individual polls required. Instead of sending separate poll messages to each STA, the AP broadcasts a single poll frame containing multiple polling messages. Each polling message corresponds to a specific STA, indicating whether it has data to transmit or not.

When a STA receives a poll message in PSMP, it can determine if it has any data to transmit. If it has data, it responds with a data frame containing the relevant information. If it doesn't have data, it can choose to remain silent, which helps conserve energy. The AP collects the responses from the STAs and initiates data transmission accordingly.

The PSMP mechanism introduces two new concepts: the Traffic Indication Map (TIM) and the Delivery Traffic Indication Message (DTIM). The TIM is a bitmap maintained by the AP that indicates which STAs have pending data to transmit. The DTIM is a special TIM that is transmitted periodically to inform the STAs about the presence of pending data.

The AP periodically transmits the DTIM frame to announce the presence of pending data to the STAs. Upon receiving the DTIM, the STAs with pending data wake up and prepare to transmit their data during the next polling round. The AP can then use PSMP to poll the STAs efficiently and retrieve the data in a single transmission.

By consolidating the polling process and optimizing the waking and sleeping patterns of STAs, PSMP reduces the overhead associated with individual polls and improves energy efficiency in Wi-Fi networks. It is particularly beneficial in scenarios with multiple STAs, especially those with sporadic or bursty traffic patterns.