701 research outputs found
Does PPP hold for Big Mac price or consumer price index? Evidence from panel cointegration
This paper examines the validity of purchasing power parity (PPP) using CPI and Big Mac prices. The benchmark model, i.e., the OLS method, which does not take nonstationarity into account, rejects the hypothesis of PPP regardless of prices used. We next use the panel cointegration method to consider the nonstationary nature of variables. Estimated results for CPI are mixed. The PPP is rejected when the nominal exchange rate is employed as the dependent variable but is not rejected when the price ratio is used as the dependent variable. By contrast, the PPP is overwhelmingly not rejected when the Big Mac price is used. Last, we remove the production bias and re-examine the same issue by using panel cointegration. The PPP is again decisively rejected when CPI price is used but not for Big Mac price. Accordingly, Big Mac price is more supportive to the validity of PPP than CPI price.Big Mac
MobiCacher: Mobility-Aware Content Caching in Small-Cell Networks
Small-cell networks have been proposed to meet the demand of ever growing
mobile data traffic. One of the prominent challenges faced by small-cell
networks is the lack of sufficient backhaul capacity to connect small-cell base
stations (small-BSs) to the core network. We exploit the effective application
layer semantics of both spatial and temporal locality to reduce the backhaul
traffic. Specifically, small-BSs are equipped with storage facility to cache
contents requested by users. As the {\em cache hit ratio} increases, most of
the users' requests can be satisfied locally without incurring traffic over the
backhaul. To make informed caching decisions, the mobility patterns of users
must be carefully considered as users might frequently migrate from one small
cell to another. We study the issue of mobility-aware content caching, which is
formulated into an optimization problem with the objective to maximize the
caching utility. As the problem is NP-complete, we develop a polynomial-time
heuristic solution termed {\em MobiCacher} with bounded approximation ratio. We
also conduct trace-based simulations to evaluate the performance of {\em
MobiCacher}, which show that {\em MobiCacher} yields better caching utility
than existing solutions.Comment: Accepted by Globecom 201
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