62 research outputs found
Information-Coupled Turbo Codes for LTE Systems
We propose a new class of information-coupled (IC) Turbo codes to improve the
transport block (TB) error rate performance for long-term evolution (LTE)
systems, while keeping the hybrid automatic repeat request protocol and the
Turbo decoder for each code block (CB) unchanged. In the proposed codes, every
two consecutive CBs in a TB are coupled together by sharing a few common
information bits. We propose a feed-forward and feed-back decoding scheme and a
windowed (WD) decoding scheme for decoding the whole TB by exploiting the
coupled information between CBs. Both decoding schemes achieve a considerable
signal-to-noise-ratio (SNR) gain compared to the LTE Turbo codes. We construct
the extrinsic information transfer (EXIT) functions for the LTE Turbo codes and
our proposed IC Turbo codes from the EXIT functions of underlying convolutional
codes. An SNR gain upper bound of our proposed codes over the LTE Turbo codes
is derived and calculated by the constructed EXIT charts. Numerical results
show that the proposed codes achieve an SNR gain of 0.25 dB to 0.72 dB for
various code parameters at a TB error rate level of , which complies
with the derived SNR gain upper bound.Comment: 13 pages, 12 figure
Resource Allocation for Heterogeneous Traffic in LTE Virtual Networks
Cellular network virtualization is being considered as a key trend in future mobile networks towards improved resource utilization. However, virtualization scenarios need investigation to understand the considerations which should be taken into account when deploying virtualized wireless networks in practice. Towards this, we address the performance of a virtualized network in the presence of heterogeneous classes of traffic. In previous cellular network virtualization literature, both Real time (RT) and Non-Real time (NRT) traffic requests have been included without distinction. Both types are provisioned using the same algorithm for allocation of resources specified by the Network Scheduler [1]. However, different types of traffic have different characteristics [2], e.g., RT requests are delay sensitive but may need fixed bandwidth, and hence should be treated differently, especially when wireless channel conditions are factored into the scheduling. We recognize this difference and in this paper, we propose a new approach to improve scheduling of resources for RT and NRT traffic. In particular, we prioritize the traffic belonging to different virtual slices from all service providers (SP/VEs) at the Network Scheduler before allocating resources to different SP/VEs, i.e., We form a Virtual Prioritized Slice (VPS). The virtual prioritized slice is forwarded to the VPS scheduler to serve all RT requests first. Only after the RT traffic is scheduled, the NRT traffic is provisioned using proportional fairness (PF) scheduling. We show by simulation results that this new VPS approach helps outperform recently proposed resource allocation schemes
A Novel Denial of Service Vulnerability in Long Term Evolution Cellular Networks
Currently many cellular networks operate using the Long Term Evolution (LTE) protocol. Therefore, most mobile subscribers interact with LTE on a daily basis, and thus are affected by the security standards and mechanisms it implements. Here, we propose a vulnerability within the LTE protocol: the mobility management control signaling, which dictates how a user equipment (UE) synchronizes with an enhanced Node-B (eNodeB) to prevent intersymbol interference. Presented are the implications and the overall effects on the bit error rate (BER) of falsified signaling which forces a UE to incorrectly advance or delay its uplink timing. Specifically, we derive a lower bound on the BER for UE that is subjected to the aforementioned signaling. Our simulation results show that a non-zero BER can be guaranteed regardless of noise conditions. Finally, we propose encryption of this signaling to prevent such an attack
Isn't Hybrid ARQ Sufficient?
In practical systems, reliable communication is often accomplished by coding
at different network layers. We question the necessity of this approach and
examine when it can be beneficial. Through conceptually simple probabilistic
models (based on coin tossing), we argue that multicast scenarios and protocol
restrictions may make concatenated multi-layer coding preferable to physical
layer coding alone, which is mostly not the case in point-to-point
communications.Comment: Paper presented at Allerton Conference 201
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