| 321. |
- Gustafsson, Harald, et al.
(författare)
-
Spectral Subtraction Using Reduced Delay Convolution and Adaptive Averaging
- 2001
-
Ingår i: IEEE transactions on speech and audio processing. - : IEEE. - 1063-6676 .- 1558-2353. ; 9:8, s. 799-807
-
Tidskriftsartikel (refereegranskat)abstract
- In handsfree speech communication the signal to noise ratio is often poor, which makes it difficult to have a relaxed conversation. By using noise suppression, the conversation quality can be improved. This paper describes a noise suppression algorithm based on spectral subtraction. The method employs a noise and speech dependent gain function for each frequency component. Proper measures have been taken to obtain a corresponding causal filter and also to ensure that the circular convolution originating from FFT filtering yields a truly linear filtering. A novel method that uses spectrum-dependent adaptive averaging to decrease the variance of the gain function is also presented. The results show a 10-dB background noise reduction for all input SNR situations tested in the range -6 to 16 dB, as well as improvement in speech quality and reduction of noise artifacts as compared with conventional spectral subtraction methods.
|
|
| 322. |
|
|
| 323. |
|
|
| 324. |
- Gustafsson, Harald
(författare)
-
Speech enhancement for mobile communications
- 2000
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Three major applications of speech enhancement have been studied: noise reduction for mobile telephone handsfree accessories, noise reduction for handheld mobile telephones, and short delay noise reduction for frame-less telephone systems. During conversation, both hearing and speaking adapt to the background noise in a noisy environment. However, when the conversation takes place over the telephone disturbances are more annoying. The disturbances are a problem since the brain will not get the extra visual and other background information when interpreting the speech. The basis for all the methods presented in this thesis is a novel spectral subtraction algorithm, a speech enhancement method. The novel method improves the conventional spectral subtraction method by introducing causal properties and reducing fluctuations of the gain filter used in spectral subtraction. Further, one extra microphone is included to improve the estimate of the background noise. Frame-less communication systems are also considered . A new spectral subtraction method, which performs the speech enhancement filtering in the time-domain.
|
|
| 325. |
|
|
| 326. |
- Gustafsson, Inger
(författare)
-
Information for transparency in transport chains
- 2004
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intermodal transports chains are complex both through its numbers of players and its number of different processes. The relationships between the players are usually settled through contractual agreements. Although the players have a common goal of providing an efficient transport chain they are also to some extent competitors, both within the chain and in other business relationships. The transport market is, like most other markets, affected by the overall informatization of society which is characterized by the fact that production tends to be information intensive. Electronic business and the focus on and development of supply chains increase pressure on effectiveness and access to information on the transportation part. At the same time the technology development and the emergence of simplified and low cost communication solutions enable improvement of processes and reduction of transaction costs with information at the core. It provides an opportunity for intermodal transports as it enables real time information to be shared between the actors and thereby improve the quality. However, implementation of ICT systems opens up new possibilities and new threats, which will have implications and consequences on the business, beyond the technical aspects and effect the power balance at all levels. This thesis sets out to contribute to the understanding of the importance of information in transport chains for achieving transparency as well as its widerimplications on the players in the transport chains. In this context transparency is defined as knowledge made accessible to all relevant players involved in the transport chain and it implies: • controllability of the common task • focusing actions on a common goal • defining the players tasks (e.g. required input and output) in the framework of a common goal all enabling a high quality transport chain.
|
|
| 327. |
- Gustafsson, Kristian, et al.
(författare)
-
E-Government : services, needs and user satisfaction
- 2004
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Within the e-government process, needs are identified and people try to come up with ideas for the public sector that will increase the effectiveness as well as lead to cost savings. Consequently, many new electronic services are being developed. As a result, Quality of Service (QoS) becomes an even more critical issue in the domain of electronic services. This paper starts by a general discussion of e-government and its services in general. Thereafter it explains different QoS factors that have been identified within the field of electronic services. The identification has been carried out by studying several researchers’ work and by experience from e-government projects. The result shows that service design, security aspects, network performance issues, as well as the users’ perspective, such as user requirements, are all factors of the QoS model. A new electronic service that does not take these factors into consideration might fail and therefore be rejected by its intended users.
|
|
| 328. |
- Gustafsson, Ronnie, et al.
(författare)
-
A Block Based Eigenvector Equalization for Time : Varying Channels
- 2002
-
Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the EigenVector Algorithm for Blind Equalization (EVA), and extend its application to the equalization of time-varying fading channels. The modified iterative algorithm, termed Block-Based EVA (BBEVA), is evaluated in terms of ISI suppression, MSE and by examining the signal constellation at the output of the equalizer. Simulation results show that the BBEVA performs better than the non-blind Least Mean Squares (LMS) algorithm.
|
|
| 329. |
- Gustafsson, Ronnie, et al.
(författare)
-
A Combined Channel Estimation Algorithm for Coherent Detection in Mobile Communication Systems
- 2002
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a coherent detection method that can reduce the estimation errors of the carrier phase resulting from Gaussian noise in communication systems where pilot symbol-assisted equalization is employed to compensate for fading distortion. The proposed approach is to use a combined algorithm consisting of the conventional feed-forward channel estimation and decision feedback channel estimation. Simulation results show that the proposed algorithm provides better performance than the conventional fading channel estimation approach.
|
|
| 330. |
|
|
