You are provided with the abstract of a scientific paper and the abstracts of the papers it references. Your task is to write a Related Work section for the main paper. This section should concisely summarize and integrate the key points from the cited abstracts, reflecting how they relate to the main paper's contributions and context. In your summary, use numerical citation markers like [1], [2], etc., to refer to the corresponding papers.

Main Abstract:
Multimedia streaming applications with stringent QoS requirements in 60GHz mmWave wireless personal area networks (WPANs) demand high rate and low latency data transfer as well as low service disruption. In this paper, we consider the problem of robust relay placement in 60GHz WPANs. Relays forward traffic from transmitter devices to receiver devices facilitating i) the primary communication path for non-line-of-sight (NLOS) transceiver pairs, and ii) secondary (backup) communication path for line-of-sight (LOS) transceiver pairs. We formulate the robust minimum relay placement problem and the robust maximum utility relay placement problem with the objective to minimize the number of relays deployed and maximize the network utility, respectively. Efficient algorithms are developed to solve both problems and have been shown to incur less service disruption in presence of moving subjects that may block the LOS paths in the environment.

Cited Abstract(s):
[1]: 60GHz is well-suited for device-to-device communication and for general in-home applications due to its huge available bandwidth. However, links at this frequency are easily degraded by environmental conditions. Indeed, the poor multipath makes it necessary to maintain good LoS (Line of Sight) paths between communicating pairs of nodes. In this paper we analyze the problem of link breakage and degradation in point-to-point 60GHz networks. We propose using repeaters to provide alternate paths between communicating nodes when the direct path degrades. The decision on which path to use is driven by the goal of maximizing data rate per connection as well as overall throughput in the network. Using extensive simulations we show that by carefully using repeaters, we can maintain Gbps rates for each pair of communicating nodes in indoor spaces. We develop an efficient distributed algorithm for allocating repeaters to links as needed and explicitly deal with the problem of interference caused by the repeaters themselves. Finally, we study the scalability of the solution with increasing numbers of communicating pairs and show that Gbps rates can be maintained even when there are as many as eight communicating pairs in a small 10mx10m room.

[2]: In this paper, we propose a spacial time slot scheduling algorithm for relay operation to improve the throughput performance of millimeter-wave wireless personal area network (mmWave WPAN) systems which employ directional antenna. The upcoming mmWave WPAN is designed for high definition TV (HDTV) transmission, high speed wireless docking and gaming, etc. Based on the fact that the significant path loss of millimeter-wave environments provides good space isolation, we have proposed a coexistence mechanism by sharing time slots for relay with direct transmission to guarantee throughput for the above data-rate-greedy applications. This paper is an extension that addresses spacial time slot scheduling for relay operation taking the effect of directional antenna into consideration. We model the throughput maximization with scheduling as an integer optimization and solve it by transforming the problem to a max-weight matching problem of a bipartite graph. We propose a scheduling algorithm based on the Kuhn-Munkres algorithm which can be used to solve the max weight matching problem. Simulation results show that there is up to 25 throughput improvement achieved compared with random scheduling method.
There are also some existing work on repeater selection and relay operation scheduling in mmWave WPANs. Repeater selection was investigated in [1] , with the objective to maximize data rate for each transmitter and receiver pair by determining the best link allocation. [2] , Lan explored time slot scheduling for relay operations in the scenario of directional antenna on mmWave devices and formulated the throughput maximization problem as an integer programming problem. However, both schemes do not consider robustness in presence of uncertain link blockage.