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In this paper, a novel enhancement of the well known ALOHA random access mechanism is presented which largely extends the achievable throughput compared to traditional ALOHA and provides significantly lower packet loss rates. The novel mechanism, called Constant Rate Assignment (CRA), is based on transmitting multiple replicas of a packet in an unslotted ALOHA system and applying interference cancellation...
Interference alignment has emerged as new tool for achieving high capacity in multi-user and multi-channel wireless interference channels. Based on maximizing a degree of freedom (DOF) metric defined for asymptotic signal to noise ratio (SNR), interference alignment encounters limitations in practical applications because of limited SNR. In addition, perfect interference alignment requires strict...
Fundamentally, benefits of Multiple Input Multiple Output (MIMO) in wireless systems rest on increasing the number of Degrees of Freedom (DoFs) that can be exploited for transmission. DoFs can be used to increase spectral efficiency and/or provide increased diversity. However, exploiting DoFs in MIMO often requires knowledge of Channel State Information (CSI) at the transmitter and/or receiver. Obtaining...
An IEEE 802.11b/g/n wireless local area network (WLAN) experiences significant radio frequency interference (RFI) from microwave ovens, cordless phones, Bluetooth, and other WLANs operating in the 2.4 GHz band. In the 2.4 GHz band, operating microwave ovens emit interference that can either prevent an access point from transmitting or cause dramatic increase in bit errors in the receiver. This paper...
Repetition-coded relaying using half-duplex relays offers an easy way of achieving cooperative diversity that works well with apparently any source transmission schemes, but at the same time presents a potentially serious problem of inefficient spectrum utilization. Poor diversity-multiplexing tradeoff (DMT) is often reported. This paper investigates efficient ways of using repetition-type decode-and-forward...
The capacity optimization problem of MIMO links with interference has attracted an increasing interest. Due to the nonconvexity of the capacity problem, only suboptimal solutions can be found. In the previous works, a Gradient Projection (GP) algorithm [1] and a Quasi-Newton (QN) method [2] were proposed to provide suboptimal solutions subject to the constant power constraint. In this paper, we derive...
In a typical macrocell network, all macrocell mobile stations (mMSs) are synchronized to the macrocell base station (mBS) during the uplink. The mMSs that are closer to the mBS transmit their signals at a later time instant so that signals of all the all mMSs arrive at the mBS at the same time. However, signals of the mMSs reach at the femtocell base stations (fBSs) with different delays, which may...
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