Centralized Channel Scheduling for 60 GHz Wireless Networks

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Solution Overview

Problem

In wireless local area networks, especially at 60 GHz, overlapped scheduling between Basic Service Sets can occur due to clock offsets and channel allocation inefficiencies, leading to beacon collisions and interference.

Innovation Solution

A centralized control mechanism allocates specific time intervals for transmit sector sweep operations, allowing wireless access points and client devices to perform directional transmissions without interfering with data transmissions by using Cluster Time Offsets and Beacon Service Periods, ensuring non-overlapping channel usage and minimizing collisions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If scheduled MAC protocol is used to allocate frequency band access, then data transmission efficiency is improved, but beacon collisions and interference occur due to clock offsets and overlapping schedules

Engineering Contradiction:

Improvedata transmission efficiencyVSAvoidbeacon transmission reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A centralized coordinator (root access point) is introduced as an intermediary to manage and synchronize beacon transmissions across the network. The coordinator assigns specific beacon intervals and time offsets to different access points, ensuring that beacons are transmitted in a coordinated manner without overlapping, thus preventing collisions while maintaining scheduled access efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Beacon intervals and time offsets are pre-assigned by the centralized coordinator before transmissions occur. This preliminary scheduling ensures that all access points know in advance when to transmit beacons, preventing clock drift and overlapping transmissions while maintaining efficient scheduled access to the frequency band

Inventive Principle:

Principle #10Preliminary action

2Area of stationary object

If multiple Basic Service Sets operate in overlapping radio ranges, then network coverage is improved, but channel interference increases due to unsynchronized transmissions

Engineering Contradiction:

Improvenetwork coverage areaVSAvoidchannel interference

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The network is segmented into multiple Basic Service Sets, each managed by a root access point that independently coordinates beacon transmissions within its domain. This segmentation allows overlapping coverage areas while maintaining synchronized transmissions within each BSS, reducing inter-BSS interference through structured time division

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Beacon transmissions are organized into periodic beacon intervals with assigned time offsets. Each access point transmits beacons at regular, predetermined intervals rather than continuously, allowing other access points to transmit during different intervals. This periodic structure enables overlapping coverage while minimizing interference through time-division multiplexing

Inventive Principle:

Principle #19Periodic action

3Adaptability or versatility

If clock offsets are allowed in wireless devices, then device synchronization flexibility is improved, but transmission timing drift occurs causing beacon overlaps

Engineering Contradiction:

Improvedevice synchronization flexibilityVSAvoidtransmission timing precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The centralized coordinator provides feedback to access points by assigning specific beacon intervals and time offsets based on current network conditions. This feedback mechanism allows the system to compensate for clock offsets and maintain precise transmission timing while still allowing devices to operate with inherent clock flexibility

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts transmission parameters (beacon intervals, time offsets, and cluster time offsets) to compensate for clock offsets in wireless devices. By changing these parameters based on assigned schedules rather than relying on fixed device clocks, the system maintains precise timing coordination while preserving device synchronization flexibility

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8817756B1Channel assignment and scheduling for centralized clustering in 60 GHz Wireless Networks

Publication Date: 2014.08.26 CISCO TECHNOLOGY INC

AI summary

Allocation schemes are provided for one or more portions of time during a data transmission time interval for contention by personal coordination points, access points and client devices to perform transmit sector sweep operations. In addition, a personal coordination point determines whether the set of channels universally agreed to be free by nearby synchronization access points is empty and selects any channel in the frequency band to initiate a Basic Service Set or continue operation of an existing Basic Service Set if it is determined that no channel in the frequency band is free among the channels that are universally agreed to be free.