Abstract
Grant-free multiple access is a critical mechanism introduced in 5G new radio (NR) to support ultra-reliable low-latency communication (URLLC) services. Pilot authentication (PA) is a key security mechanism to guarantee reliable performance of grant-free URLLC. However, PA can be easily paralyzed by pilot-aware attack since pilot signals are usually publicly known, and unprotected. To solve this, we develop the concatenated graph coding (CGC) theory by which time-frequency resources on bandwidth part (BWP) can be encoded flexibly to protect PA securely. Particularly, we use bipartite graph, and multigraph theory to model PA on BWP as transmission, and retrieval of pilot (TRP). Each transmitter in the uplink needs transmit a unique random pilot sequence as subcarrier activation pattern (SAP) on BWP. After observing SAPs from multiple transmitters, the receiver decodes a pilot sequence of interest, and tests its authenticity. The retrievability of authentic pilots is defined, and formulated analytically. We also derive the analytical closed-form expression of system failure probability, and accessibility in the regime of large-scale antenna arrays, and short data packets. Interestingly, we find that four trade-offs exist: retrievability-latency, retrievability-accessibility, reliability-latency, and reliability-accessibility. Simulation results show the security advantage of our proposed theory in grant-free URLLC system.
Highlights
5G networks are expected to support mission-critical applications demanding ultra-reliable and low-latency communications (URLLC), like industrial automation, remote control, health monitoring and tactile Internet [1], [2]
In an uplink scenario of grant-free URLLC, user equipment (UE) can transmit data in a pre-configured bandwidth part (BWP) that comprises of time, frequency and pilots, and data transmission is performed without the request/grant procedure
If we examine the information security in 5G new radio (NR), message authentication in grant-free URLLC plays a critical role since it guarantees the integrity, authenticity, and non-repudiation of messages that flow over the air [8], [9]
Summary
On one hand, current PA schemes rely on a SAP-encoded methodology for which “multidimensional resources, parallelism and coding” become their keywords. The allowable resources might be limited and cannot provide a suitable basis for the method This make us to rethink: whether or not it is possible to encode grant-free time-frequency physical resources to protect pilot authentication of multiple UEs operating flexibly in BWP with very high reliability and low latency. The configuration information of SSB and those BWPs on the whole channel bandwidth can be decoded in SRB0 in high layer Those information include but not limited to the location and size of SSB and BWPs. In RRCconnected state, grant-free URLLC occurs and occupies the grant-free physical resource pool within the first active BWP. We will detail the models of random pilots, TRP, channel estimation and data transmission
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