As new features are introduced into the Bluetooth core specification, the ability to use Bluetooth Low Energy (BLE) technology to construct a mobile ad-hoc network (MANET) becomes a reality. Key features included in Bluetooth Specification version 4.1 are the ability for a single node to be part of multiple piconets, and the ability for a node to act dual mode, as both a piconet master and slave. These features allow the possibility of multi-hop routing spanning multiple connected piconets. Although multi-hop routing is theoretically possible with version 4.1, no multi-hop routing algorithm has never been presented which exploits this possibility. In this paper we propose an approach to scatternet formation and multi-hop routing for networks using BLE version 4.1. We define procedures for device discovery, communication between piconets and forming multi-hop scatternet. Our approach has the following properties, 1) it can be used with existing Bluetooth hardware, 2) the protocol is fully distributed, so global connectivity information is not required for formation and routing, and 3) it supports ad-hoc network formation. We have implemented our approach using real Bluetooth SoCs including the Broadcom BCM434x chipset which is used in the iPhone 6. Our experiments demonstrate the routing delay and throughput using networks containing different numbers of nodes in order to demonstrate the impact of network size on performance. As the network size increases, our protocol does not incur a large delay and achieves better resource utilization.

We present a spreading gain adaptation protocol between a transmitter and a receiver communicating with each other through a direct-sequence spread spectrum system. This protocol does not require the transfer of an explicit control message indicating the change of spreading gain from the transmitter to the receiver. Also, according to this protocol, the transmitter can change the spreading gain "symbol by symbol" (SBS) as opposed to "frame by frame" (FBF); this enables extremely fast adaptation to the time-varying wireless channel and/or to the rate variation of the traffic. The proposed scheme uses the orthogonal variable spreading factor (OVSF) codes to enable the receiver to detect the spreading gain used by the transmitter. Our analysis indicates that fast adaptation can significantly improve the average throughput over a slow or no adaptation.

We design a forest with nodes that represent orthogonal variable spreading factor (OVSF) sequences of different lengths (spreading codes of different lengths that can be used for multi-rate DS-CDMA). In addition to the non-descendant OVSF property exhibited in well-known tree-structured generation of sequences [(F. Adachi, et al., 1997) and (E.H. Dinan and B. Jabbari, 1998)], the sequences represented by the nodes of our forest have useful properties that can be used to achieve multi-channel communication (with a sequence providing a channel) with a lower total peak-to-mean envelope power ratio (PMEPR). These OSVF sequences grouped by our forest structure also have properties that facilitate symbol-by-symbol adaptation of the symbol duration in multi-rate CDMA systems. For example, certain lineages in the forest have the property that any pair of code sequences in the same lineage are shift orthogonal to each other, with the unit shift length being that of the shorter sequence. We present the forest-structured generation of the sequences (spreading codes) and their properties.

We present a closed-loop architecture and protocols for rapid dynamic spreading gain adaptation and fast feedback between a transmitter and a receiver communicating with each other in CDMA networks. These protocols and architecture do not require the transfer of an explicit control message indicating the change of CDMA spreading gain from transmitter to receiver. Also, with these protocols, the transmitter can change the spreading gain symbol-by-symbol as opposed to frame-by-frame, and feedback information (e.g., the fast-varying channel condition) can be exchanged almost as frequently as the symbol rate; thus, faster adaptation to the time-varying channel conditions of wireless networks and/or the rate variation of traffic is possible than with the existing frame-by-frame approach.

We analyze the symbol error rate of a multiple-branch predetection maximal ratio combiner for correlated Nakagami-m-fading channels. Focusing on the correlations between diversity branches, we provide a simple analytic proof, applicable to different modulation schemes, that uncorrelated branches result in the lowest symbol error probability. First, we present a proof assuming that all branches have the same fading severity m, where m can be a noninteger. We then present a proof for the case where the branches have different but, integer-valued fading severities (ms).

We introduce a forest whose nodes represent orthogonal variable spreading factor (OVSF) code sequences of different lengths used for multi-rate CDMA. These code sequences have properties that facilitate symbol rate adaptation and blind rate detection, which can be used in a fast time-varying environment such as mobile communication systems. The properties of these codes also makes flexible the assignment of code sequences of different lengths to different users who communicates at different constant symbol rates. In particular, certain lineages in the forest have a property that the set of code sequences represented by such a lineage are cyclic orthogonal to each other with unit length being that of the shortest sequence in the set. We present the forest-structured generation of the code sequences and their properties. Then, we present a symbol rate adaptation protocol and a blind rate detection algorithm that use the code properties.

We further simplify the numerically friendly bit-error rate expression presented by Simon and Alouini (see ibid., vol.46, p.1625-38, 1998) for noncoherent and differentially coherent systems with multichannel reception over additive white Gaussian noise and generalized fading channels.

We refine the exact expressions of the average symbol error rate (SER) of several coherent, L-branched maximal-ratio-combining (MRC) receivers in a set of correlated Nakagami-m (1960) fading channels with additive white Gaussian noise (AWGN). These expressions can be applied to study the performance for M-PSK or M-QAM receivers with any number of diversity branches, with an arbitrary SNRs correlation function between branches, with any constellation size, and with any fading severity parameter m rational. In addition, we analyze the channel capacity of the M-PSK system with MRC receivers for the case of balanced branches (i.e. all branches have the same average SNR per symbol) for arbitrary SNR correlation functions. The results of this analysis can guide the design in realizing the systems that dynamically adapt modulation schemes to the time-varying channel conditions in order to maintain the data link's quality of service (QoS).