Femto Cell Short Signal Transmission via Tone-Symbol Position Coding
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Solution Overview
Problem
Femto cell and peer to peer devices interfere with macro base station communications when using the same air link resources, causing interference and impacting macro cell throughput, especially when transmitting short signals like control information or discovery signals.
Innovation Solution
Femto cell and peer to peer devices identify resource blocks used by the macro base station and transmit information on a limited number of available tone-symbols, using position coding to minimize interference by avoiding tone-symbols used for pilot signals and communicating at high power levels on a small number of tone-symbols within resource blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If femto cell devices and peer to peer devices transmit short signals at relatively high power on the same communications resources as macro base station, then the reliability of short signal transmission is improved, but the macro cell throughput deteriorates due to interference with base station pilots and control signals
Solution Approach 1:
The patent applies local quality by designating specific resource blocks within the macro cell for femto cell and peer to peer device transmissions. Instead of allowing high power transmissions across all resources, the system allocates particular time-frequency resources where these transmissions are permitted, creating localized zones of permitted interference that do not overlap with critical macro base station pilots and control signals.
Solution Approach 2:
The patent segments the available communications resources into distinct categories: resources dedicated to macro base station pilots and control signals, and resources available for femto cell and peer to peer transmissions. This segmentation is achieved through resource block allocation and signaling that divides the time-frequency spectrum into protected regions and shared regions, preventing interference while enabling short signal transmissions.
2Adaptability or versatility
If femto cell devices and peer to peer devices are not directly controlled by the base station to limit interference, then the device autonomy is improved, but the interference control capability deteriorates
Solution Approach 1:
The patent implements preliminary action by having the macro base station pre-allocate and pre-signal specific resource blocks that are designated for femto cell and peer to peer device transmissions. This advance allocation establishes clear boundaries and permissions before devices begin autonomous operations, enabling them to transmit without real-time base station control while ensuring they operate within interference-safe zones.
Solution Approach 2:
The patent enables self-service by allowing femto cell devices and peer to peer devices to autonomously select and transmit on the pre-designated resource blocks without requiring continuous base station scheduling or control. Devices independently utilize the allocated resources for their short signal transmissions, achieving autonomy while the pre-established resource allocation prevents harmful interference.
Data Source
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AI summary
Methods and apparatus for communicating short messages from a first device, e.g., a femto cell device or peer to peer device, over communications resources which are being used by an OFDM macro network, e.g., cellular network, are described. The signal goes on top of, e.g., is transmitted on the same communications resource(s), on which a macro signal, e.g. a downlink signal from a cellular base station, is transmitted. Since the signals from the femto cell and/or peer to peer devices are transmitted on the same resources as the signals from the macro base station, they interfere with the macro signal and potentially destroy a portion of the macro signal. However, the signals transmitted by the femto cell devices and/or peer to peer devices are designed so that they cause little interference to the macro base station in terms of overall throughput and/or with the macro base station's ability to communicate control and/or pilot information.