Hashed SSID BSSID PHY Layer Scanning
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Solution Overview
Problem
Conventional scanning methods in IEEE 802.11 wireless networks are time-consuming, requiring up to 2 seconds in the 2.4 GHz band and 3 seconds in the 5 GHz band to complete a channel scan, due to processing at the MAC layer, which delays the identification of SSID/BSSID information.
Innovation Solution
Generating a hashed SSID or BSSID using a hashing function applied to the access point's ID combined with channel information, reducing the number of data bits and transmitting it within a physical layer frame, allowing for faster identification and association by stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional scanning methods are used at the MAC layer, then complete channel scanning can be performed, but the scanning time is excessive (2-3 seconds)
Solution Approach 1:
The patent segments the SSID/BSSID identification process from the MAC layer to the PHY layer. By placing the hashed SSID/BSSID in the PHY layer preamble (specifically in the SIG field or reserved bits), the identification function is separated from the time-consuming MAC layer scanning process, enabling parallel processing and reducing overall scanning time.
Solution Approach 2:
The patent applies preliminary action by pre-computing and embedding the hashed SSID/BSSID into the PHY layer frames before transmission. This allows stations to perform identification during the physical layer reception process itself, rather than waiting for MAC layer processing after complete frame reception, thereby advancing the identification step forward in the protocol stack.
2Loss of information
If SSID/BSSID information is transmitted in full form, then complete identification information is provided, but the data transmission overhead increases
Solution Approach 1:
The patent transforms the SSID/BSSID parameter by applying a hashing function that converts the original variable-length SSID or 48-bit BSSID into a fixed-length hashed value (e.g., 8-16 bits). This parameter transformation maintains the uniqueness and identification capability while dramatically reducing the bit length, thus reducing transmission overhead without losing essential identification information.
Solution Approach 2:
The patent creates a condensed copy of the SSID/BSSID information through hashing. Instead of transmitting the full SSID or BSSID, a hashed copy is generated that preserves the essential identification properties (uniqueness and matchability) while occupying significantly less space, allowing efficient comparison and identification with minimal data transmission.
Data Source
AI summary
An access point (AP) hashes its SSID/BSSID according to a hashing function H and transmits wirelessly the hashed SSID/BSSID within a physical layer frame/packet to a user station (STA). The hashed SSID/BSSID uniquely identifies the AP. In one embodiment, the hashed SSID/BSSID is transmitted within a SIGNAL field of a preamble with the frame/packet. Upon receipt, the user station recovers the hashed SSID/BSSID and compares it to an expected hashed SSID/BSSID (calculated using the same hashing function H and a desired SSID/BSSID). In response to the comparison, the user station performs one or more actions.