In the present work, a methodology has been proposed to design analog/mixed-signal circuits using digital-in-concept circuits in digital technology. This paper presents a digital standard cell-based, scalable, highly synthesizable analog voltage comparator designed in 180 nm CMOS technology at the supply voltage of 1.8 V. The digital design requires less design effort and is highly immune to process, voltage and temperature variations. The proposed comparator has been designed and simulated in the Cadence virtuoso analog design environment. It is observed from the simulation results that the total power dissipation and propagation delay is 143.2 μW and 1.07 ns, respectively. The offset voltage of the proposed comparator is 4.98 mV. Also, as a proof-of-concept, the feasibility of the proposed analog voltage comparator is carried out on Artix-7 field-programmable gate array (FPGA) using Xilinx Basys-3 FPGA kit and other off-the-shelf components. The proposed digital-in-concept comparator is suitable for low power and high-speed SoC application with reduced design effort and lesser time-to-market.

Growing popularity of high-speed wireless broadband access for real-time applications makes it increasingly relevant to study the admission control and scheduling of flows in a service differentiated manner. Next-generation wireless broadband networks employ orthogonal frequency division multiple access (OFDMA) technology that enables multiple users to communicate at the same time using a time-frequency grid. In this paper, we provide a mathematical model for prioritized admission control and scheduling in OFDMA-based multihop wireless networks. The problem is formulated as an integer linear program (ILP) that does joint admission control and scheduling of flows while satisfying its rate and latency requirements. We propose different heuristic algorithms for scheduling priority-based flows in centralized multihop OFDMA networks. We define the “Flow Admittance” (FA) metric and compare the different scheduling schemes based on this metric. Simulation results show that the Start from Frame Beginning (SFB) heuristic performs well in most of the scenarios. We also propose a combination approach that merges multiple heuristics. The FA values obtained from the combination approach are close to the ILP while incurring computation time orders of lower magnitude.

In this paper we propose an adaptive scheduling algorithm for IEEE 802.16j based wireless broadband networks. Computation of an optimal schedule for prioritized traffic in OFDMA based IEEE 802.16 wireless network is an NP-Hard problem. Hence, we propose a scheduling heuristic for an OFDMA based WiMAX relay network. The ORS (OFDMA Relay Scheduler) heuristic computes the zone boundaries (relay and access) in an uplink scheduling frame based on the number of RSs and MSs, the bandwidth demands and the link conditions. The ORS heuristic determines a schedule which assigns subchannels and timeslots to prioritized traffic based on the demand for various nodes while implementing frequency selectivity. The ORS adapts zone boundaries and the schedule to link and demand conditions at every scheduling period. We perform extensive simulations to demonstrate the effectiveness of adaptive zone scheduling and changes in rate conditions for various topologies.

Multi-hop WiMAX networks based on IEEE 802.16 has the potential of easily providing high-speed wireless broadband access to areas with little or no existing wired infrastructure. WiMAX technology can be used as "last mile" broadband connections to deliver streaming audio or video to clients. Thus, quality of service (QoS) is very important for WiMAX networks. Providing QoS in multi-hop WiMAX networks such as WiMAX mesh or mobile multi-hop relay networks is challenging as multiple links can interfere with each other if they are scheduled at the same time. We propose efficient heuristic algorithms for scheduling flows in a centrally scheduled multi-hop WiMAX network. The proposed algorithms guarantee bandwidth and delay constraints of flows and allow multiple non-interfering links to be scheduled at the same time. We also define a "schedule efficiency" metric for comparing different flow scheduling algorithms. The simulation results show that the "schedule flow subchannel" algorithm leads to the best schedule efficiency.

In many applications of sensor networks, security is a very important issue. To be resistant against the various attacks, nodes in a sensor network can establish pairwise secret keys[5], [6], [10], authenticate all communications with cryptographic functions[8], and also apply secure information aggregation schemes[13] or hop-by-hop filtering methods[14], [16]. However, these security measures can take considerable overhead in terms of storage, communication and computation, which are scarce resources in sensor nodes. Previously proposed security measures can only resist against a limited number of compromised nodes, which we define as the resistance level. In this paper, we propose a separate solution to any security measure. This technique either significantly reduces the overhead, or increases the resistance level without increasing overhead. The solution is based on a new "Mixed Multi-Channel" (MMC) architecture. In this design, each node can only use one fixed channel. The whole network is thus divided into multiple "planes" by the different planes. Exploiting the characteristics of multi-channel communication, a series of methods are proposed, such as MMC-1, MMC-k and MMC-r. We then present designs to integrate the methods with current security measures, and analyze their resistance level and energy conservation.

A data warehouse is a collection of data from different sources that supports analytical querying. A Bitmap Index (BI) allows fast access to individual attribute values that are needed to answer a query by representing the values of an attribute for all tuples separately, as bit strings. A Property Map (PMap) is a multidimensional indexing technique that pre-computes attribute expressions, called properties, for each tuple and stores the results as bit strings [DD97, LD02]. This paper compares the performance of the PMap and the Range-Encoded Bit-Sliced Index (REBSI) [CI98] using cost models to simulate their storage and query processing costs for different kinds of queries over a benchmark schema. We identify parameters that affect performance of these indexes and determine situations in which either technique gives significant improvement over the other. We also explore ways to improve PMap design to enhance performance.