Narrowband internet of things (NB-IoT) is a recent cellular radio access technology based on Long-Term Evolution (LTE) introduced by Third-Generation Partnership Project (3GPP) for Low-Power Wide-Area Networks (LPWAN). The main aim of NB-IoT is to support massive machine-type communication (mMTC) and enable low-power, low-cost, and low-data-rate communication. NB-IoT is based on LTE design with some changes to meet the mMTC requirements. For example, in the physical (PHY) layer only single-antenna and low-order modulations are supported, and in the Medium Access Control (MAC) layers only one physical resource block is allocated for resource scheduling. The aim of this survey is to provide a comprehensive overview of the design changes brought in the NB-IoT standardization along with the detailed research developments from the perspectives of Physical and MAC layers. The survey also includes an overview of Evolved Packet Core (EPC) changes to support the Service Capability Exposure Function (SCEF) to manage both IP and non-IP data packets through Control Plane (CP) and User Plane (UP), the possible deployment scenarios of NB-IoT in future Heterogeneous Wireless Networks (HetNet). Finally, existing and emerging research challenges in this direction are presented to motivate future research activities.

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Narrowband Internet of Things (NB-IoT): From Physical (PHY) and Media Access Control (MAC) Layers Perspectives

This paper presents a novel and robust chaos-based cryptosystem for secure transmitted images and four other versions. In the proposed block encryption/decryption algorithm, a 2D chaotic map is used to shuffle the image pixel positions. Then, substitution (confusion) and permutation (diffusion) operations on every block, with multiple rounds, are combined using two perturbed chaotic PWLCM maps. The perturbing orbit technique improves the statistical properties of encrypted images. The obtained error propagation in various standard cipher block modes demonstrates that the proposed cryptosystem is suitable to transmit cipher data over a corrupted digital channel. Finally, to quantify the security level of the proposed cryptosystem, many tests are performed and experimental results show that the suggested cryptosystem has a high security level.

A New Chaos-Based Cryptosystem for Secure Transmitted Images

Techniques for adjusting transmit timing of base stations and user equipments (UEs) in a wireless network are described. In one operating scenario, a femto base station communicates with a femto UE, and a macro base station communicates with a macro UE located within the coverage of the femto base station. In an aspect, the transmit timing of the femto base station may be delayed relative to the transmit timing of the macro base station, e.g., to time align downlink signals from the femto and macro base stations at the femto and macro UEs. In another aspect, the transmit timing of the femto UE may be advanced relative to the transmit timing of femto base station by an amount larger than twice the propagation delay between the femto UE and the femto base station, e.g., to time align uplink signals from the femto and macro UEs at the femto base station.

Timing adjustment for synchronous operation in a wireless network

Method and apparatus to perform channel estimation for a wireless communication system are described.

Channel estimation for a wireless communication system

Embodiments may define traffic priorities to facilitate transmissions for wireless communications devices. Many embodiments comprise MAC sublayer logic to generate and transmit management frames such as beacon frames, association response frames, reassociation response frames, and probe response frames with an access category for low power consumption stations or sensor stations comprising a parameter record defining a contention window that is the earliest contention window to open amongst contention windows defined for the access categories for traffic. In some embodiments, the MAC sublayer logic may store the parameter record sets for access categories in memory, in logic, or in another manner that facilitates transmission of the frames. Some embodiments may receive and detect communications with frames comprising the access categories and store a parameter set for one or more of the access categories in a management information base.

Methods and arrangements for channel access in wireless networks

In the uplink of an OFDMA system, a preamble is used to estimate a channel and then the pilot tones of a data symbol are used for channel estimation to update the channel estimate. The channel estimate is used for channel compensation, and the phase of the channel is corrected using the channel estimate obtained from the pilot tones. In this way, the channel estimation performance and hence the compensation ability can be enhanced.

Uplink channel estimation system for orthogonal frequency division multiple access system and method thereof

When a base station of a time division duplex based mobile communication system receives an initial ranging request signal from a subscriber station, the base station generates initial ranging information including delay time information to the subscriber station, and receives uplink data delayed and transmitted using a delay time from the subscriber station. Also, when the subscriber station transmits an initial ranging request signal to the base station and receives initial ranging information including delay time information from the base station, the subscriber station establishes a transmission parameter value by using the transmission parameter value included in the initial ranging information and transmits uplink data by using the established delay time.

Method and apparatus for uplink timing synchronization with ranging signal in mobile communication system

Disclosed is an AGC (automatic gain control) device and method of an OFDM system with a DC offset compensation function, and a recording medium storing a program including the method. The AGC device calculates an energy of input signals with DC offsets as the summation of the square of the input signals, and calculates an energy of the DC offsets in the input signals as the summation of the square of the DC offsets. Pure signal energy without DC offsets is produced by subtracting the energy of the DC offsets from the energy of the calculated input signal. The energy and an AGC reference value are then compared, and feedback of a comparison result is performed.

Automatic gain control device and method in orthogonal frequency division multiplexing system with DC offset compensation function, and recording medium storing program containing the method

Disclosed is a ranging system and method in an OFDMA system. The ranging system includes complex exponential twiddle storage units for respectively storing complex exponential twiddle factors corresponding to a timing error, complex multipliers for respectively complex-multiplying the complex exponential twiddle factors by received uplink ranging data, code correlators for respectively correlating the outputs of the complex multipliers and ranging codes, and threshold comparators for respectively comparing the outputs of the code correlators with a threshold.

Uplink ranging system and method in OFDMA system

The present invention relates to a method of detecting a candidate vector and a method of detecting a transmission symbol using the same. According to an embodiment of the present invention, in a multiple input multiple output (MIMO) system using spatial multiplexing (SM), a receiver selects candidate vectors corresponding to a layer located at a last row among a plurality of rearranged layers, and sequentially ranks constellation dots of a next layer for each of the selected candidate vectors. Then, a plurality of arbitrary constellation dots are selected from the ranked constellation dots, accumulated costs of the arbitrary constellation dots are calculated, and a candidate vector is selected in correspondence with a constellation dot having a minimal accumulated cost. Then, a new arbitrary constellation dot is selected in place of the constellation dot selected as the candidate vector, an accumulated cost of the selected arbitrary constellation dot is compared with accumulated costs of the other arbitrary constellation dots, and another candidate vector is selected.

Young-Ha Lee

Papers

Uplink channel estimation system for orthogonal frequency division multiple access system and method thereof

Method and apparatus for uplink timing synchronization with ranging signal in mobile communication system

Automatic gain control device and method in orthogonal frequency division multiplexing system with DC offset compensation function, and recording medium storing program containing the method

Uplink ranging system and method in OFDMA system

Method of selecting candidate vector and method of detecting transmission symbol