Full Duplex Joint Communications and Sensing for 6G: Opportunities and Challenges

The diagram shows how signals from Cell B's base station and UL users can be leveraged by Cell A for improved sensing performance, while maintaining communication functions.

New Full Duplex System Could Enhance 6G Networks and Sensing

A new approach to 6G wireless technology enables simultaneous transmission and reception of data on the same frequency band while improving sensing capabilities. The system, detailed in a paper from researchers at multiple European institutions, combines full duplex joint communications and sensing (JCAS) technology.

The system allows base stations to transmit and receive data simultaneously, potentially doubling spectral efficiency compared to current systems. It integrates both monostatic radar, where transmitter and receiver are co-located, and multiple bistatic radars to enhance object detection and tracking.

The researchers address self-interference challenges, where transmitted signals can overpower received signals by up to 110 decibels, through a three-stage approach: passive suppression, analog cancellation, and digital cancellation.

The system incorporates security features using artificial noise generation to protect communication data and sensing information. Test results indicate improved sensing accuracy when combining monostatic and multiple bistatic radar capabilities.

Technical challenges remain in areas including waveform design, channel state estimation, and signal processing optimization as the technology develops toward practical implementation.

Research Team and Affiliations:
- University of Luxembourg: Chandan Kumar Sheemar, Sourabh Solanki, Eva Lagunas, Jorge Querol, Symeon Chatzinotas, and Bjorn Ottersten
- National and Kapodistrian University of Athens: George C. Alexandropoulos

The team collaborated on system design, theoretical analysis, and performance evaluation, combining expertise in wireless communications, radar systems, and signal processing. 

Paper Summary

This paper presents opportunities and challenges for full duplex joint communications and sensing (JCAS) systems in 6G networks. Key points:

Core Innovation:

• - Enables simultaneous transmission/reception on same frequency band
• - Combines monostatic radar (at base station) with multiple bistatic radars (from uplink users)
• - Could double spectral efficiency while enhancing sensing capabilities

Technical Features:

• - Addresses self-interference through three-stage cancellation
• - Leverages uplink users' signals for additional bistatic radar sensing
• - Enables low-latency multi-user communications
• - Incorporates security through artificial noise generation

Key Challenges Identified:

• - Waveform design and beamforming
• - Channel state estimation
• - Signal processing and data fusion
• - Multi-objective optimization
• - Security implementation
• - THz wideband operation

Results:

• - Numerical tests show improved sensing accuracy when combining monostatic and bistatic radar capabilities
• - Performance gains demonstrated at different SINR levels (-5dB and 5dB)
• - Benefits increase with number of uplink users/bistatic radars

The paper provides a comprehensive framework for next-generation JCAS systems while highlighting important research directions for practical implementation.

Figures and Tables

Figures in Paper:

1. Benchmark JCAS architectures (Fig. 1)

•    - Shows three cases: DL-only, UL-only, and combined UL/DL scenarios
•    - Used to illustrate evolution of JCAS configurations

2. Proposed JCAS system (Fig. 2)

•    - Depicts FD BS, UL/DL users, monostatic/bistatic radar setup
•    - Illustrates interference patterns and signal paths

3. Cooperative JCAS diagram (Fig. 3)

Key Innovation: Instead of treating Cell B's signals as pure interference, Cell A exploits them as additional bistatic radar sources for enhanced target detection. This represents a shift from traditional interference management to cooperative sensing.

The diagram specifically shows how signals from Cell B's base station and UL users can be leveraged by Cell A for improved sensing performance, while maintaining communication functions.

•    - Shows cooperation between two cells (A and B)
•    - Demonstrates inter-cell interference and radar opportunities

4. Optimization methodology flowchart (Fig. 4)

•    - Shows iterative process for optimizing JCAS performance
•    - Outlines adaptation steps for DL/UL variables and filters

5. MSE performance graph (Fig. 5)
   - Plots MSE vs number of bistatic radars/uplink users
   - Compares performance at different SINR levels

Figure 5 plots the Mean Square Error (MSE) in dB against the number of bistatic radars/uplink users (0-10) under two different signal-to-interference-plus-noise ratio (SINR) conditions: 5dB and -5dB.

The graph compares two approaches:
1. Traditional monostatic-only radar sensing
2. Combined monostatic and multi-bistatic radar sensing

Key findings:
- MSE improves (decreases) as more bistatic radars are added
- Combined approach outperforms monostatic-only at both SINR levels
- Performance degrades at lower SINR (-5dB vs 5dB)
- Greatest improvements occur with first few added bistatic radars
- Benefits continue but diminish with additional radars

The results demonstrate quantitative evidence for the benefits of combining monostatic and bistatic radar approaches in JCAS systems, particularly in terms of direction-of-arrival estimation accuracy.

Full Duplex Joint Communications and Sensing for 6G: Opportunities and Challenges

Computer Science > Information Theory

[Submitted on 14 Aug 2023 (v1), last revised 21 Nov 2024 (this version, v2)]

Chandan Kumar Sheemar, Sourabh Solanki, George C. Alexandropoulos, Eva Lagunas, Jorge Querol, Symeon Chatzinotas, Björn Ottersten

The paradigm of joint communications and sensing (JCAS) envisions a revolutionary integration of communication and radar functionalities within a unified hardware platform. This novel concept not only opens up unprecedented interoperability opportunities, but also exhibits unique design challenges. To this end, the success of JCAS is highly dependent on efficient full-duplex (FD) operation, which has the potential to enable simultaneous transmission and reception within the same frequency band. While JCAS research is lately expanding, there still exist relevant directions of investigation that hold tremendous potential to profoundly transform the sixth generation (6G), and beyond, cellular networks. This article presents new opportunities and challenges brought up by FD-enabled JCAS, taking into account the key technical peculiarities of FD systems. Unlike simplified JCAS scenarios, we delve into the most comprehensive configuration, encompassing uplink and downlink users, as well as monostatic and bistatic radars, all harmoniously coexisting to jointly push the boundaries of both communications and sensing. The performance improvements resulting from this advancement bring forth numerous new challenges, each meticulously examined and expounded upon.

Subjects:	Information Theory (cs.IT); Signal Processing (eess.SP)
Cite as:	arXiv:2308.07266 [cs.IT]
	(or arXiv:2308.07266v2 [cs.IT] for this version)
	https://doi.org/10.48550/arXiv.2308.07266

Submission history

From: Chandan Kumar Sheemar [view email]
[v1] Mon, 14 Aug 2023 16:50:12 UTC (2,648 KB)
[v2] Thu, 21 Nov 2024 13:27:43 UTC (23,008 KB)