Multi-beam Antenna Array Capacity Pilot Interference
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Solution Overview
Problem
Current digital cellular systems, such as CDMA and UMTS, face challenges in maximizing base station capacity to serve a large number of mobile devices efficiently, especially in areas where reducing the number of base stations is desirable due to cost and site availability constraints.
Innovation Solution
Implementing a multi-beam antenna array system where coded timeslots are transmitted on each beam, with the same overhead channels, including a pilot channel, shared across all beams, and different data traffic transmitted using the same codes on each beam, leveraging spatial separation to discriminate between beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple narrow beams are used to increase capacity, then base station capacity is improved, but pilot channel interference may occur
Solution Approach 1:
The patent applies local quality by assigning different code sequences to different narrow beams for pilot channel transmission. Each beam uses a locally distinct code, allowing the system to maintain multiple simultaneous beams without pilot channel interference, thereby increasing base station capacity while avoiding harmful interference effects.
2Productivity
If the same codes are re-used across different beams, then data traffic transmission efficiency is improved, but beam discrimination difficulty increases
Solution Approach 1:
The patent resolves this contradiction by applying local quality: data traffic channels use the same codes across beams for efficiency, while pilot channels use different local codes for each beam. This allows the mobile station to discriminate between beams through pilot channel identification while maintaining efficient code reuse for data transmission.
Solution Approach 2:
The patent segments the channel functions by separating pilot channel transmission from data traffic transmission. Pilot channels use beam-specific codes for identification and discrimination, while data traffic channels reuse codes across beams for efficiency. This segmentation allows both goals to be achieved simultaneously.
Data Source
AI summary
A cellular communication system comprising a plurality of geographically spaced base stations (2) each of which comprises an antenna arrangement (4, 6, 8) per base station sector, each of which antenna arrangements has an antenna element for generating an array of narrow beams (10, 12, 14) covering the sector. Timeslots are simultaneously transmitted over each of the beams so as to generate successive sets of simultaneously transmitted timeslots per sector. The timeslots are each split into multiple orthogonal codes, for example Walsh codes. The communication system additionally comprising a scheduling device (31) for allocating for successive sets of timeslots common overhead channels, including a common pilot channel, which are allocated to the same sub-set of codes of each timeslot in the set. For successive sets of timeslots different data traffic is allocated to the same sub-set of codes of each timeslot in the set. This effectively generates a sector wide antenna beam carrying the common overhead channels and a plurality of narrow beams each of which carry different data traffic. Inter-beam interference is addressed by the application of Adaptive Modulation and Coding and by an inter-beam handoff scheme. The handoff scheme ensures that when an end user equipment is located in a cusp region between adjacent beams the antenna arrangement simultaneously transmits data traffic to that mobile station on at least both of the adjacent beams.