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Jianjun Wu

Bio: Jianjun Wu is an academic researcher from Peking University. The author has contributed to research in topics: Communications satellite & Wireless network. The author has an hindex of 5, co-authored 11 publications receiving 53 citations.

Papers
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Proceedings ArticleDOI
08 Dec 2011
TL;DR: The foundation for the application of adaptive transmission in GEO mobile satellite communications is established accordingly and the predictability of the satellite channel is discussed associated with the channel correlation results.
Abstract: Channel prediction is the premise for the application of adaptive transmission in mobile satellite communications with long propagation delay. Particularly, in GEO mobile satellite communication systems, the satellite channel correlation characteristics are analyzed for the mobile terminals at different positions and along different directions, and the predictability of the satellite channel is discussed associated with the channel correlation results. The foundation for the application of adaptive transmission in GEO mobile satellite communications is established accordingly.

9 citations

Patent
10 Oct 2012
TL;DR: In this article, a handover switching method of a user terminal under a single-hop mode in a satellite communication system, belonging to the technical field of satellite communication, is described.
Abstract: The invention discloses a handover switching method of a user terminal under a single-hop mode in a satellite communication system, belonging to the technical field of satellite communication The method of the invention comprises the following steps: (a) a wireless network controller of a user terminal sends a single-hop resource reconfiguration message to a satellite routing controller and simultaneously starts a double-hop switching process required by signaling; (b) the satellite routing controller judges whether single-hop resources are available or not, wherein if the single-hop resources are available, the wireless network controller indicates the satellite routing controller to execute single-hop resource reallocation and indicates the user terminal to carry out physical channel reconfiguration, and if no single-hop resources are allocated, the wireless network controller indicates the satellite routing controller to release current single-hop resources and indicates the terminal to carry out physical channel reconfiguration according to a double-hop link physical channel message; (c) the satellite routing controller informs the satellite to execute operation; and (d) the wireless network controller completes the ground network operation required by handover switching of the user terminal The invention can be used for satellite mobile communication

5 citations

Patent
25 Aug 2010
TL;DR: In this article, a voice transit method for a satellite mobile communication system, belonging to the technical field of satellite communication, is presented, where a double-hop voice connection between a target calling party and atarget called party is established, and a single hop voice connection is transited to the double-Hop voice connection.
Abstract: The invention discloses a voice transit method for a satellite mobile communication system, belonging to the technical field of satellite communication. The satellite mobile communication system comprises a communication network main body branch and an on-satellite switching management control branch. The method comprises that: a) a double hop voice connection between a target calling party and atarget called party is established; b) a single hop voice connection between the target calling party and the target called party is transited to the double hop voice connection; and c) a new single hop voice connection between the calling party and the called party is established. The method can be used for the satellite mobile communication.

5 citations

Proceedings ArticleDOI
08 Dec 2011
TL;DR: The influence of other spot-beam interference value is shown by an example of network design, which shows the mobile satellite system compatible with TD-SCDMA should use frequency reuse factor 1.
Abstract: In this paper, other spot-beam interference value is studied based on a mobile satellite system (MSS) compatible with TD-SCDMA by theoretical analysis and numerical simulation. A system model to calculate the interference value is presented by making assumptions such as perfect power control and uniformly distributed users. Numerical results of other spot-beam interference value with different frequency reuse factors and different spot-beam overlap values are obtained. Additionally, the influence of other spot-beam interference value is shown by an example of network design, which shows the mobile satellite system compatible with TD-SCDMA should use frequency reuse factor 1.

5 citations


Cited by
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Patent
28 Apr 2016
TL;DR: In this article, the handoff of a user terminal to a different satellite involves the user terminal conducting satellite signal measurements and sending a measurement message to the satellite network portal, whereby, based on this information, the satellite portal generates the satellite handoff information and/or selects a handoff procedure for the user.
Abstract: Various aspects of the disclosure relate to handoff of a user terminal in communication with a satellite network portal through a satellite. In some aspects, a satellite network portal and a user terminal use a satellite handoff information to determine when to handoff the user terminal from one cell to another and/or from one satellite to another. In some aspects, a user terminal sends capability information, location information, or other information to a satellite network portal whereby, based on this information, the satellite network portal generates the satellite handoff information and/or selects a handoff procedure for the user terminal. In some aspects, handoff of a user terminal to a different satellite involves the user terminal conducting satellite signal measurements and sending a measurement message to the satellite network portal. In some aspects, the satellite network portal generates new satellite handoff information as a result of receiving a measurement message.

62 citations

Patent
Dankberg Mark1
26 Jul 2016
TL;DR: In this article, in-flight configuration of satellite pathways to flexibly service terra-link and cross-link traffic in a constellation of non-processed satellites, for example, to facilitate flexible forward-channel and return-channel capacity in a satellite communications system.
Abstract: Embodiments provide in-flight configuration of satellite pathways to flexibly service terra-link and cross-link traffic in a constellation of non-processed satellites, for example, to facilitate flexible forward-channel and return-channel capacity in a satellite communications system. For example, each satellite in the constellation can include one or more dynamically configurable pathway, and switching and/or beamforming can be used to configure each pathway to be a forward-channel pathway or a return-channel pathway in each of a number of timeslots according to a pathway configuration schedule. At least some of the pathways can be further selectively configured, in each timeslot, to carry "terra-link" traffic to and/or from terrestrial terminals and "cross-link" traffic to and/or from one or more other satellites of the constellation.

36 citations

Journal ArticleDOI
TL;DR: Compared with the traditional uniform resource allocation or proportional resource allocation algorithms, the proposed optimal power allocation algorithm improves the fairness of power allocation amongst the users.
Abstract: In recent years, multi-spot-beam satellite communication systems have played a key role in global seamless communication. However, satellite power resources are scarce and expensive, due to the limitations of satellite platform. Therefore, this paper proposes optimizing the power allocation of each user in order to improve the power utilization efficiency. Initially the capacity allocated to each user is calculated according to the satellite link budget equations, which can be achieved in the practical satellite communication systems. The problem of power allocation is then formulated as a convex optimization, taking account of a trade-off between the maximization of the total system capacity and the fairness of power allocation amongst the users. Finally, an iterative algorithm based on the duality theory is proposed to obtain the optimal solution to the optimization. Compared with the traditional uniform resource allocation or proportional resource allocation algorithms, the proposed optimal power allocation algorithm improves the fairness of power allocation amongst the users. Moreover, the computational complexity of the proposed algorithm is linear with both the numbers of the spot beams and users. As a result, the proposed power allocation algorithm is easy to be implemented in practice.

18 citations

Patent
28 Aug 2013
TL;DR: In this article, an example system for satellite payload communications including a digital channelizer and a regenerative communications subsystem (RCS) is presented, where the RCS is configured to process selected ones of the plurality of signals to produce processed signals.
Abstract: An example system for satellite payload communications includes a digital channelizer and a regenerative communications subsystem (RCS). The digital channelizer includes a plurality of inputs for receiving a plurality of signals from a plurality of uplink beams and a plurality of outputs for outputting the plurality of signals. The RCS includes a plurality of inputs selectably coupled to the digital channelizer outputs to receive signals from selected ones of the digital channelizer outputs and a plurality of outputs selectably coupled to the digital channelizer inputs to transmit the processed signals to selected ones of the digital channelizer inputs. The RCS is configured to process selected ones of the plurality of signals to produce processed signals.

14 citations

Proceedings ArticleDOI
27 Mar 2014
TL;DR: A two-step time delay difference estimation scheme is proposed for orthogonal frequency division multiple access (OFDMA) multi-beam satellite system and shows good performance.
Abstract: In initial random access, base station (BS) estimates the distance between the user equipment (UE) and BS. In the mobile satellite system (MSS), however, the characteristics of large transmission delay makes the estimation method used in the terrestrial system not applicable in the MSS. To solve this problem, a two-step time delay difference estimation scheme is proposed for orthogonal frequency division multiple access (OFDMA) multi-beam satellite system. We first divide a beam cell into some layered small sub-areas according to the different delay difference values. Then, two types of Physical Random Access Channel (PRACH) preamble burst format are performed: the first one is for the fractional delay difference value measurement and the second one is for the integer part. Further, complete criteria for the designation of PRACH parameters are proposed and closed-form expressions of the system performance are also derived, including the false alarm probability and the missed detection probability. Finally, according to the numerical analysis, the method shows good performance.

13 citations