  We study a multi-access variant of the popular coded caching framework, which
consists of a central server with a catalog of $N$ files, $K$ caches with
limited memory $M$, and $K$ users such that each user has access to $L$
consecutive caches with a cyclic wrap-around and requests one file from the
central server's catalog. The server assists in file delivery by transmitting a
message of size $R$ over a shared error-free link and the goal is to
characterize the optimal rate-memory trade-off. This setup was studied
previously by Hachem et al., where an achievable rate and an
information-theoretic lower bound were derived. However, the multiplicative gap
between them was shown to scale linearly with the access degree $L$ and thus
order-optimality could not be established.
  A series of recent works have used a natural mapping of the coded caching
problem to the well-known index coding problem to derive tighter
characterizations of the optimal rate-memory trade-off under the additional
assumption that the caches store uncoded content. We follow a similar strategy
for the multi-access framework and provide new bounds for the optimal
rate-memory trade-off $R^*(M)$ over all uncoded placement policies. In
particular, we derive a new achievable rate for any $L \ge 1$ and a new lower
bound, which works for any uncoded placement policy and $L \ge K/2$. We then
establish that the (multiplicative) gap between the new achievable rate and the
lower bound is at most $2$ independent of all parameters, thus establishing an
order-optimal characterization of $R^*(M)$ for any $L\ge K/2$. This is a
significant improvement over the previously known gap result, albeit under the
restriction of uncoded placement policies. Finally, we also characterize
$R^*(M)$ exactly for a few special cases.
