LTE-U WLAN Coexistence via Protocol Preamble Detection
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Solution Overview
Problem
The coexistence of LTE-U and WLAN systems in the same frequency band is challenging due to potential collisions, leading to reduced system throughput, as existing mechanisms for coordination are inadequate, especially when LTE-U devices do not have WLAN capabilities and rely on energy detection, which can be unreliable in fluctuating environments.
Innovation Solution
Implementing a mechanism where LTE-U devices send a WLAN message to quiet the medium before transmitting, using energy detection or RTS-CTS to ensure the medium is clear, and employing a WLAN subsystem to detect protocol preambles and generate messages that reserve the frequency band for LTE-U operation, allowing non-WLAN devices to operate without interference from WLAN devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LTE-U devices use energy detection to check medium availability, then device complexity is reduced, but reliability of medium access deteriorates due to unreliable detection in fluctuating environments
Solution Approach 1:
The patent introduces a WLAN subsystem as an intermediary component within the LTE-U device. This subsystem includes a protocol preamble detector and a message generator that creates WLAN-format reservation messages. The intermediary translates LTE-U's simple energy detection into a more reliable WLAN-protocol-based medium reservation mechanism, resolving the contradiction between device complexity and access reliability.
Solution Approach 2:
The patent implements preliminary action by having the LTE-U device send a WLAN-format reservation message before actual data transmission. This message reserves the medium for a specified duration, preventing collisions with WLAN devices. The reservation message is sent in advance, allowing the LTE-U device to secure medium access rights before competing transmissions occur.
2Device complexity
If LTE-U devices transmit without coordination mechanisms, then system simplicity is maintained, but system throughput deteriorates due to collisions with WLAN devices
Solution Approach 1:
The patent applies universality by enabling the LTE-U device to operate with dual functionality: it maintains its LTE-U protocol operations while simultaneously using WLAN protocol formats for medium reservation. The WLAN subsystem generates messages in WLAN format that can be understood by both WLAN devices and the LTE-U device itself, allowing coordinated operation across different protocol domains without sacrificing system simplicity.
3Reliability
If LTE-U devices send WLAN reservation messages, then medium access reliability is improved, but use of energy increases due to additional message transmission
Solution Approach 1:
The patent implements partial action by sending WLAN reservation messages only when necessary - specifically, when the LTE-U device intends to transmit data and needs to reserve the medium. The reservation message duration is set to match the expected transmission time, avoiding excessive messaging. This selective approach maintains reliability while minimizing additional energy consumption compared to continuous messaging.
Data Source
AI summary
In some aspects, the disclosure is directed to methods and systems for protocol coexistence. Within a frequency band of a wireless local area network (WLAN), a device implemented for operation in at least a non-WLAN protocol can determine that the frequency band is quiet at a first time instance. The device can transmit a message in WLAN protocol responsive to the determination and prior to operation in the non-WLAN protocol within the frequency band. The message can have a receiver address other than an address belonging to other devices operating within the frequency band.