Signal Design for Future Telecommunication and Radar Systems - Isis Project No 3707
A new code sequence family – orthogonal polyphase spreading sequence - eliminates Multi-user Interference and provides excellent resilience to Doppler frequency shift for spread spectrum communications systems and radar systems.
Marketing Opportunity
The Oxford invention has applications preferably but not exclusively in commmunication systems for military, avionics and civil uses. Applications include:
- Mobile terminals
- Wireless Local Area Networks
- High-resolution Ranging, such as Global Positioning System (GPS)
- Radar Systems
The Oxford invention aims to cater for the strong growth of multimedia services in communication devices that will require networks with higher data transmission rates and greater capacity, driving the demand for Evolved High Speed Packet Access (HSPA+), Long-term evolution (LTE), Fourth Generation and Worldwide Interoperability for Microwave Access (Wimax and Wimax II) technologies.
The Oxford Invention
Spreading sequences are used to spread signal energy over a larger bandwidth in the frequency domain. The performance of spreading sequences is measured by their ability to reduce multi-user interference through orthogonality and their Doppler resilience. Currently, orthogonal pseudo random codes such as Walsh-Hadamard Spreading Sequence (WHSS), lose orthogonality when two spread signals experience a time delay due to varying or unexpected signal paths, or are Doppler shifted between transmission and reception.
The Oxford invention is a new family of polyphase spreading codes with enhanced orthogonality properties. The sequences have perfect “zero” periodic cross-correlation under any non-zero time delay shifts. The invention has several advantages:
- Elimination of Multi-user Interference
- Excellent Doppler shift resilience
- Transmission power saving during uplink or downlink transmissions
Figure 1 compares the periodic cross-correlation of Oxford Sequence to the conventional WHSS sequence. Over time delay shift t, the Oxford sequence shows a flat zero-value response in comparison to WHSS, where significant side lobes are attributed to the origin of undesired interference between signals in the communications system.
| a |  |
| b |  |
| Figure 1: The Oxford sequence (a) shows excellent cross correlation properties in comparison to WHSS (b). |
Patent Status
This work is the subject of a UK patent application, and Isis would like to talk to companies interested in commercialising this opportunity. Please contact the Isis Project Manager to discuss this further.
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