OFDM Base Station Frequency-Multiplexing Broadcast Unicast Traffic
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Solution Overview
Problem
Conventional OFDM networks waste power during unicast traffic transmissions due to increased interference from neighboring cells, as higher power transmission does not improve SINR for unicast traffic, and available power cannot be adaptively allocated between unicast and broadcast traffic, leading to system inefficiency.
Innovation Solution
Frequency-multiplexing of broadcast and unicast traffic in the downlink allows for adaptive power allocation between the two, enabling simultaneous transmission and improving spectral efficiency by sharing unused power between unicast and broadcast traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher power transmission is used for unicast traffic, then transmit power increases, but SINR does not improve due to increased interference from neighboring cells
Solution Approach 1:
The patent segments the frequency spectrum into dedicated unicast subcarriers and broadcast subcarriers. By separating unicast and broadcast traffic in the frequency domain rather than time domain, the system allows simultaneous transmission while enabling independent power allocation. This segmentation resolves the contradiction by allowing power to be allocated to broadcast subcarriers without interfering with unicast SINR performance.
Solution Approach 2:
The patent transitions from time-division multiplexing (one dimension) to frequency-division multiplexing (another dimension). By allocating different subcarriers for unicast and broadcast traffic within the same time slot, the system enables adaptive power allocation across frequency resources. This dimensional change allows broadcast power to be increased without degrading unicast SINR, as they occupy orthogonal frequency resources.
2Power
If power is allocated to unicast traffic, then unicast transmission is maintained, but broadcast traffic cannot utilize available power due to time-multiplexing constraints
Solution Approach 1:
The patent merges unicast and broadcast traffic transmission into the same time slot by allocating different frequency subcarriers to each. This combining allows the system to simultaneously serve both unicast and broadcast users, enabling adaptive power allocation where unused unicast power can be allocated to broadcast subcarriers. The merging resolves the contradiction by eliminating the time-multiplexing constraint that previously prevented broadcast power allocation.
Solution Approach 2:
The patent creates a universal frequency resource allocation framework where subcarriers can be dynamically assigned for unicast or broadcast purposes based on traffic demands. The base station can adaptively allocate power across both unicast and broadcast subcarriers within the same TTI, making the system versatile in handling different traffic conditions. This multi-functionality resolves the contradiction by allowing power to serve dual purposes of maintaining unicast quality while enabling broadcast transmission.
3Device complexity
If time-multiplexing is used for broadcast and unicast traffic, then transmission simplicity is maintained, but power utilization is wasted due to inability to allocate power adaptively
Solution Approach 1:
The patent introduces dynamic power allocation across frequency subcarriers within the same time slot. The base station can adaptively adjust power distribution between unicast and broadcast subcarriers based on channel conditions and traffic demands. This dynamic approach resolves the contradiction by maintaining the simple time-slot structure while adding frequency-domain flexibility that eliminates power waste through adaptive allocation.
Solution Approach 2:
The patent changes the allocation parameters from time-based (TTI-level) to frequency-based (subcarrier-level). By allocating power at the subcarrier level rather than at the TTI level, the system achieves fine-grained power control that eliminates waste. This parameter change resolves the contradiction by maintaining transmission simplicity at the TTI level while introducing flexible frequency-domain power allocation to prevent energy loss.
Data Source
AI summary
A base station for use in an orthogonal frequency division multiplexing (OFDM) wireless network capable of communicating with a plurality of subscriber stations in a coverage area of the OFDM wireless network. The base station is capable of transmitting a first OFDM symbol in a first time slot, wherein the first OFDM symbol comprises a first plurality of subcarriers used to transmit broadcast data directed to a plurality of subscriber stations and a second plurality of subcarriers used to transmit unicast data directed to at least one selected subscriber station.