| 1. |
- Andersson, Göran, et al.
(författare)
-
Energy efficient heterogeneous network deployment with cell DTX
- 2016
-
Ingår i: 2016 IEEE International Conference on Communications (ICC). - : IEEE. - 9781479966646 ; , s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- This paper evaluates different means of reducing power consumption of macro base stations (BS) and heterogeneous mobile network deployments (HetNet) considering the time dimension. These approaches are based on the same idea of reducing the load of heavily loaded macro cells and putting them to discontinuous transmission (DTX) mode during the time of inactivity by either (1) macro cell densification or (2) offloading traffic to small cells. Activity factor of a BS is defined as the fraction of time the BS is transmitting over a fixed time period. It is shown that by macro cell layer network densification, the average daily area power consumption can be reduced by up to 73 % with the use of cell DTX. However, reducing the activity factor by macro layer densification is not cost effective, as already demonstrated in previous studies. Alternatively, by adding small cells and enabling their DTX capability, power consumption can be reduced by up to 29 %. Adding small cells is especially effective in terms of energy savings, when users are distributed around hot spots, where additional coverage and capacity is required.
|
|
| 2. |
- Arshad, Malik Wahaj, et al.
(författare)
-
Energy efficiency gains through traffic offloading and traffic expansion in joint macro pico deployment
- 2012
-
Ingår i: 2012 IEEE Wireless Communications and Networking Conference, WCNC. - : IEEE Communications Society. - 9781467304375 ; , s. 2203-2208
-
Konferensbidrag (refereegranskat)abstract
- The traffic demand in future mobile cellular networks is expected to increase exponentially which would lead to dense base station deployment and eventually higher energy consumption. The current dominant mobile systems including GSM and UMTS were not designed with focus on energy efficiency. This paper investigates the energy saving potential of pico nodes in a heterogeneous network from an incumbent operator consideration. The results show that the number of hotspots and the user distribution in the hotspots strongly effects the power saving. Also, sleep modes in pico base stations have shown to reduce the energy loss to almost half. On a day average with limited utilization of pico base station, the heterogeneous network scenario provides marginal saving. The results also show that if the pico base station resources are fully utilized, premium user case, the heterogeneous network scenario can provide substantial reduction in energy per bit.
|
|
| 3. |
- Arshad, Malik Wahaj, et al.
(författare)
-
Energy efficiency improvement through pico base stations for a green field operator
- 2012
-
Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. - : IEEE Communications Society. - 9781467304375 ; , s. 2197-2202
-
Konferensbidrag (refereegranskat)abstract
- Mobile telecommunication operators are now focussing on emerging markets due to the current highly competitive mobile telecommunication sector in established markets. The deployment of wireless mobile infrastructure in these emerging markets or a green field scenario requires an innovative energy efficient approach, which is not feasible in an incumbent operator scenario. This paper describes a combined macro and pico cellular heterogeneous wireless network architecture, and analyses its energy efficiency with respect to variation in inter site distance. The increase in capacity and power saving through sparse network deployment is investigated in terms of area spectral efficiency and area power consumption respectively. The results suggest that the deployment of pico cells along with a traditional cellular network can improve the energy efficiency of the network, as well as provide gains in terms of increased inter site distance. Finally. the indifference curves of Energy Efficiency and number of pico nodes indicate the optimum deployment scheme for multiple area spectral efficiency targets.
|
|
| 4. |
- Blom Västberg, Oskar, 1987-, et al.
(författare)
-
A dynamic discrete choice activitybased travel demand model
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- During the last decades, many activity-based models have been developed in the literature. However, especially in random utility based models timing decisions are often treated poorly or inconsistently with other choice dimensions. In this paper we show how dynamic discrete choice can be used to overcome this problem. In the proposed model, trip decisions are made sequentially in time, starting at home in the morning and ending at home in the evening. At each decision stage, the utility of an alternative is the sum of the one-stage utility of the action and the expected future utility in the reached state.The model generates full daily activity schedules with any number of trips that each is a combination of one of 6 activities, 1240 locations and 4 modes. The ability to go from all to all locations makes evaluating the model very time consuming and sampling of alternatives were therefore used for estimation. The model is estimated on travel diaries and simulation results indicates that it is able to reproduce timing decisions, trip lengths and distribution of the number trips within sample.To explain when people perform different activities, two sets of parameters are used: firstly, the utility of being at home varies depending on the time of day; and secondly, constants determine the utility of arriving to work at specific times. This was enough to also obtain a good distribution of the starting times for free-time activities.
|
|
| 5. |
- Blom Västberg, Oskar, 1987-, et al.
(författare)
-
A joint between-day and within-day activity based travel demand with forward looking individuals
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Including day-to-day planning to account for systematic variability in activity participation has the potential to further improve travel demand models. This paper introduce a dynamic discrete choice model of day-to-day and within-day planning in a joint framework. No model up to date jointly treats within-day and day-to-day planning with individuals that take future days into account. The model is estimated using a combination of a small survey with week long data and a larger single day travel survey. A static, myopic and forward looking version of the model is estimated. There is a big improvement in model fit when moving from a static to a dynamic model, but allowing forward-looking behaviour gives a relatively small additional improvement. As a policy test, grocery stores are closed on Sundays. The myopic model predicts that people as a consequence will shop more on Mondays-Thursdays and therefore unintuitively also less on Saturdays. The forward looking model also predicts increased shopping on weekdays but mainly that people will shop more on Saturdays anticipating that stores are closed on Sundays.
|
|
| 6. |
- Blom Västberg, Oskar, 1987-, et al.
(författare)
-
Discount factors greater than or equal to one in infinite horizon dynamic discrete choice models
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, the theory on infinite horizon DDCM's is extended to allow for discount factors greater than or equal to one. The proposed methods are applied to Rust's (1987) bus engine replacement model, where a discount factor of 1.075 is identified using grid search. The infinite horizon problem with and without a terminal state are treated separately. Sufficient conditions are given for the existence of solutions to Bellman's equation in the terminal state problem and to a normalized version of Bellman's equation in the non-terminal state setting. If a terminal state exists, acting according to Bellman's equation still yields the maximum expected total utility under derived conditions on the one-stage utility functions and reachability of the terminal state. In the non-terminal state problem, $\beta=1$ implies that individuals maximize the average cost per stage, but for $\beta>1$ no rationale for acting according to Bellman's equation, even when it has a solution, has been found.
|
|
| 7. |
- Blom Västberg, Oskar, 1987-
(författare)
-
Five papers on large scale dynamic discrete choice models of transportation
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Travel demand models have long been used as tools by decision makers and researchers to analyse the effects of policies and infrastructure investments. The purpose of this thesis is to develop a travel demand model which is: sensitive to policies affecting timing of trips and time-space constraints; is consistent with microeconomics; and consistently treats the joint choice of the number of trips to perform during day as well as departure time, destination and mode for all trips. This is achieved using a dynamic discrete choice model (DDCM) of travel demand. The model further allows for a joint treatment of within-day travelling and between-day activity scheduling assuming that individuals are influenced by the past and considers the future when deciding what to do on a certain day.Paper I develops and provides estimation techniques for the daily component of the proposed travel demand model and present simulation results provides within sample validation of the model. Paper II extends the model to allow for correlation in preferences over the course of a day using a mixed-logit specification. Paper III introduces a day-to-day connection by using an infinite horizon DDCM. To allow for estimation of the combined model, Paper III develops conditions under which sequential estimation can be used to estimate very large scale DDCM models in situations where: the discrete state variable is partly latent but transitions are observed; the model repeatedly returns to a small set of states; and between these states there is no discounting, random error terms are i.i.d Gumble and transitions in the discrete state variable is deterministic given a decision.Paper IV develops a dynamic discrete continuous choice model for a household deciding on the number of cars to own, their fuel type and the yearly mileage for each car. It thus contributes to bridging the gap between discrete continuous choice models and DDCMs of car ownership.Infinite horizon DDCMs are commonly found in the literature and are used in, e.g., Paper III and IV in this thesis. It has been well established that the discount factor must be strictly less than one for such models to be well defined.Paper V show that it is possible to extend the framework to discount factors greater than one, allowing DDCM's to describe agents that: maximize the average utility per stage (when there is no discounting); value the future greater than the present and thus prefers improving sequences of outcomes implying that they take high costs early and reach a potential terminal state sooner than optimal.
|
|
| 8. |
- Farias, Fabricio S., et al.
(författare)
-
Green backhauling for heterogeneous mobile access networks : What are the challenges?
- 2013
-
Ingår i: 2013 9th International Conference on Information, Communications and Signal Processing (ICICS). - : IEEE Computer Society. - 9781479904334 ; , s. 6782868-
-
Konferensbidrag (refereegranskat)abstract
- Heterogeneous network (HetNet) deployment strategies have the potential to improve the energy efficiency of mobile access networks. One key aspect to consider in HetNets is the impact of the power consumption of the backhaul, i.e., the overall energy efficiency of a HetNet deployment is affected by the backhaul technology and architecture. This paper presents a preliminary assessment of the design challenges of a future green backhaul segment for a HetNet deployment. The study is based on the analysis of the medium term future outlook (i.e., between now and the year 2025) of the main technologies used in todays'* backhaul networks (i.e., fiber, microwave and copper). It can be concluded that, even if there arc no doubts that both microwave and fiber will be predominately used in the future, the possible migration paths leading to such fiber- and microwave-dominated scenarios might be different, depending on factors such as spectrum and license costs, time to deployment, availability of equipment, and required Quality of Service (QoS) levels.
|
|
| 9. |
- Glerum, Aurélie, et al.
(författare)
-
A dynamic discrete-continuous choice model of car ownership, usage and fuel type
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a dynamic discrete-continuous choice model of car ownership, usage, and fuel type that embeds a discrete-continuous choice model into a dynamic programming framework to account for the forward-looking behavior of households in the context of car acquisition. More specifically, we model the transaction type, the choice of fuel type, and the annual driving distance for up to two cars in the household. We present estimation and cross-validation results based on a subsample of the Swedish population that is obtained from combining the population and car registers. Finally we apply the model to analyze a hypothetical policy that consists of a subsidy that reduces the annual cost of diesel cars.
|
|
| 10. |
- Miao, Guowang, et al.
(författare)
-
Energy Efficiency in the Wideband Regime
- 2013
-
Ingår i: 2013 IEEE Wireless Communications And Networking Conference (WCNC). - : IEEE Communications Society. - 9781467359399 ; , s. 510-515
-
Konferensbidrag (refereegranskat)abstract
- In this paper we discuss globally optimal energy-efficient communications in the wideband regime that is characterized by wide signal bandwidth and low spectral efficiency. An end-to-end multiple-hop system with one sender, one receiver, and multiple relays is considered. We discover the globally optimal link adaptation as well as relay deployment strategies such that the whole system can run with the highest energy efficiency. The technologies proposed can be used in various communication systems, such as the deployment and communication of wired core networks and wireless broadband relay backhauls, to improve their energy efficiency.
|
|
