Ju Wook Jang

Application of network coding to IEEE 802.16j mobile multi-hop relay network for throughput enhancement

We observe simultaneous transmission of relay stations (RSs) allowed in current IEEE 802.16j draft standard for multi-hop relay networks may involve severe interference among the RSs, hence leading to throughput degradation. Allowing only 1/3 of the RSs to simultaneously transmit instead of 1/2 RSs as in the current draft standard reduces the interference but results in reduced throughput. To remedy this problem, we devise schemes to incorporate network coding at link-layer level (decode-and-forward) into the simultaneous transmission of RSs. Data movement is rearranged to maximize coding gain. Formula is derived to dictate exact movement of packets traveling between base station (BS) and mobile stations (MSs) via intermediate RSs. The frame structure in the current IEEE 802.16j draft standard does not allow broadcast needed for network coding. We devise a new frame structure which supports the broadcast. A new R-MAP (pointers to the burst data) is introduced to implement the broadcast. Since our new frame structure is used only for BS to RS or RS to RS communication, our schemes retain backward compatibility with legacy MSs based on IEEE 802.16e standard. Simulation based on simple configuration of RSs shows considerable improvement in terms of system throughput and round trip delay. For a 4-hop relay network with 1 BS and 4 RSs with symmetric traffic in uplink (UL) and downlink (DL), throughput is improved by 49% in DL and by 84% in UL traffic compared with IEEE 802.16j draft standard under the assumption that omni-directional antennae are used in BS and RSs.

Enhanced throughput and QoS fairness for two-hop IEEE 802.16j relay networks

Frequency reuse among relay stations (RSs) in a down- link access zone is widely adopted for throughput enhancement in IEEE 802.16j relay networks. Since the areas covered by the RSs or the base station (BS) may overlap, some mobile stations (MSs) at the border between two neighboring transmitting stations (RS or BS) using an identical frequency band may suffer severe interference or outage. This co-channel interference within the cell degrades the quality of service (QoS) fairness among the MSs as well as the system throughput. Exclusive use of a frequency band division (orthogonal resource allocation) among RSs can solve this problem but would cause degradation of the system throughput. We observe a trade-off between system through- put and QoS fairness in the previously reported schemes based on frequency reuse. In this paper, we propose a new frequency reuse scheme that achieves high system throughput with a high fairness level in QoS, positioning our scheme far above the trade-off curve formed by previous schemes. We claim that our scheme is beneficial for applications in which a high QoS level is required even for the MSs at the border. Exploiting the features of a directional antenna in the BS, we create a new zone in the frame structure. In the new zone, the RSs can serve the subordinate MSs at the border and prone to interference. In a 3-RS topology, where the RSs are located at points 120° apart from one another, the throughput and Jain fairness index are 10.64 Mbps and 0.62, respectively. On the other hand, the throughput for the previously reported overlapped and orthogonal allocation schemes is 8.22 Mbps (fairness: 0.48) and 3.99 Mbps (fairness: 0.80), respectively. For a 6-RS topology, our scheme achieves a throughput of 18.38 Mbps with a fairness of 0.68; however, previous schemes with frequency reuse factors of 1, 2, 3, and 6 achieve a throughput of 15.24 Mbps (fairness: 0.53), 12.42 Mbps (fairness: 0.71), 8.84 Mbps (fairness: 0.88), and 4.57 Mbps (fairness: 0.88), respectively.

Data Managing and Service Exchanging on IoT Service Platform Based on Blockchain with Smart Contract and Spatial Data Processing

Expectation of cryptocurrencies has been increased rapidly and all of these cryptocurrencies are generated on blockchain platform. This means not only the paradigm is changing in the field of finance but also the blockchain platform is technically stable. Based on the stability of blockchain, many kind of crypto currencies or application platforms are being implemented or released and world famous banks are applying blockchain on their financial service[1]. Even law for exchanging cryptocurrencies is being discussed. Furthermore, blockchain platforms also run programmed source code which is called as smart contract on its distributed platform. Smart contract extends usage of blockchain platform. So in this paper, we propose an algorithm for recording and managing location data of IoT service provider and user based on blockchain with smart contract. Our proposal records data of participants in network by blockchain which ensures security and match with other optimized participant by spatial data processing.

Improved throughput for wireless backhaul networks configured in a linear array of wireless relays

The biggest obstacle to achieving high throughput for wireless backhaul networks is co-channel interference. We devise a new transmission scheme that overcomes this and achieves high throughput. Our scheme coordinates the transmission of downstream packets and upstream packets to employ network coding (NC). It allows every second relay transmit for enhanced throughput and overcomes the resulting co-channel interference through successive interference cancellation (SIC). Simulation results show our scheme excels the state-of-the-art by as much as 124.9% in terms of throughput and 33% in terms of exchange latency.