NTT DoCoMo

About: NTT DoCoMo is a based out in . It is known for research contribution in the topics: Base station & Mobile station. The organization has 4032 authors who have published 8655 publications receiving 160533 citations.

Model T: an empirical model for user registration patterns in a campus wireless LAN

Abstract: We derive an empirical model for spatial registration patterns of mobile users as they move within a campus wireless local area network (WLAN) environment and register at different access points. Such a model can be very useful in a variety of simulation studies of the performance of mobile wireless systems, such as that of resource management and mobility management protocols. We base the model on extensive experimental data from a campus WiFi LAN installation, representing traces from about 6000 users over a period of about 2 years. We divide the empirical data available to us into training and test data sets, develop the model based on the training set, and evaluate it against the test set.The model shows that user registration patterns exhibit a distinct hierarchy, and that WLAN access points (APs) can be clustered based on registration patterns. Cluster size distributions are highly skewed, as are intra-cluster transition probabilities and trace lengths, which can all be modeled well by the heavy-tailed Weibull distribution. The fraction of popular APs in a cluster, as a function of cluster size, can be modeled by exponential distributions. There is general similarity across hierarchies, in that inter-cluster registration patterns tend to have the same characteristics and distributions as intra-cluster patterns.We generate synthetic traces for intra-cluster transitions, inter-cluster transitions, and complete traces, and compare them against the corresponding traces from the test set. We define a set of metrics that evaluate how well the model captures the empirical features it is trying to represent. We find that the synthetic traces agree very well with the test set in terms of the metrics. We also compare the model to a simple modified random waypoint model as a baseline, and show the latter is not at all representative of the real data.The user of the model has the opportunity to use it as is, or can modify model parameters, such as the degree of randomness in registration patterns. We close with a brief discussion of further work to refine and extend the model.

Slot assignment algorithm

Abstract: The present invention provides scheduling algorithms that guarantee minimum data transport service for even ATs with poor channel conditions. Data-requesting ATs are divided into a number (N g1 ) of AT groups according to their channel conditions. Also, a recurring sequence of time slots is defined on the TDMA channel and partitioned into a number (N g2 ) of slot groups, where N g2 is made larger than N g1 . Generally, slot assignment according to the present invention is a two-step process. First, in the sequence, the slot groups are allocated to the AT groups so that AT groups with better channel conditions will receive more slot groups while each AT group will receive at least one slot group. Second, in each AT group, the time slots allocated to an AT group are assigned to the individual ATs in the group. By assigning more slot groups to AT groups with better channel conditions, the algorithm will optimize the overall data throughput. By assigning at least one slot group to each AT groups, the algorithm will guarantee minimum service to ATs with poor channel conditions.

Spectral Efficiency Improvement With 5G Technologies: Results From Field Tests

Abstract: Spectral efficiency is always a key factor to be improved and optimized along mobile communication networks evolving generation by generation. 5G enabling technologies must take spectral efficiency into consideration. In this paper, we show the performance of three key 5G technologies in sense of spectral efficiency improvement. Sparse code multiple access, polar codes, and filtered orthogonal frequency-division multiplexing are novel multiple access technology, channel coding scheme, and waveform, respectively. The combination of them is implemented in a 5G field trial testbed by NTT DOCOMO and Huawei for the first time. According to the field test results, we achieve over 100% spectral efficiency improvement comparison with baseline, where orthogonal frequency-division multiple access and turbo coding as LTE are used.

Packet transmission method and system, and packet transmitting apparatus, packet receiving apparatus, and packet transmitting/receiving apparatus

Abstract: A packet transmission method for transmitting packets classified according to a quality of service (QoS) requirement from a transmitting node to a receiving node is provided. In the transmitting node, the steps of: selecting sequentially a QoS class; dividing a queued packet to be transmitted belonging to the selected class into a plurality of predetermined data units, and transmitting one of the obtained predetermined data units; and applying a transmitter-side retransmission control process to the data unit to be transmitted when the selected class is a QoS class specified for data type packets are provided. In the receiving node, the steps of: receiving sequentially the data units transmitted from the transmitting node; assembling a plurality of received data units to decompress the original packet for each QoS class; and applying a receiver-side retransmission control process to the received data units to be assembled when the received data unit belongs to one of the QoS classes specified for the data type packets are provided.

Data-Center Architecture Impacts on Virtualized Network Functions Service Chain Embedding with High Availability Requirements

Abstract: Network Functions Virtualization (NFV) is a recent networking trend gaining a lot of attention from telecom operators and vendors. It promises to virtualize entire classes of network node functions within a data-center and to deliver network services in the form of Virtualized Network Function (VNF) service chains using commercial off-the-shelf hardware and IT virtualization technologies. However, availability gets an important issue when purpose-built telecom hardware designed for the "fives nines" standard via built-in failure protection and recovery mechanisms is replaced by the off-the shelf hardware. With commercial off-the-shelf data-center hardware, failure probabilities could be higher than in traditional physical network infrastructure. Thus with NFV, infrastructure availability has to be considered all the way from the physical right up to the hypervisor layer and resilience mechanisms need to be built into the software and service provisioning design. In this work, we model different backup strategies for VNF service chains and provide algorithms for their resilient embedding in the data-center. Further, we answer the question which data-center topologies offer the best cost-per-throughput relation for a given resilience/availability for VNF service chains.